Method of mineral oil production

ABSTRACT

The present invention relates to a method for producing mineral oil from underground mineral oil deposits, in which an aqueous formulation comprising at least a mixture of alkyl ether carboxylate and corresponding alkyl ether alcohol, where the alkyl ether carboxylate has been prepared from the alkyl ether alcohol and the molar ratio in the mixture of alkyl ether carboxylate:alkyl ether alcohol is from 51:49 to 92:8, is injected through at least one injection well into a mineral oil deposit, where the deposit has a deposit temperature of 55° C. to 150° C., a crude oil having more than 20° API and a deposit water having more than 100 ppm of divalent cations, and crude oil is withdrawn through at least one production well from the deposit. The invention further relates to the preparation of the mixture and to a concentrate comprising the mixture.

The present invention relates to a method for producing mineral oil fromunderground mineral oil deposits, in which an aqueous saline surfactantformulation comprising at least a mixture of alkyl ether carboxylate andalkyl ether alcohol, where the alkyl ether carboxylate has been preparedfrom the alkyl ether alcohol and the molar ratio in the mixture of alkylether carboxylate:alkyl ether alcohol is from 51:49 to 92:8 and theconcentration of all the surfactants together is 0.05% to 0.49% byweight based on the total amount of aqueous saline surfactantformulation, is injected through at least one injection well into amineral oil deposit having a deposit temperature of 55° C. to 150° C.,crude oil having more than 20° API and deposit water comprising morethan 100 ppm of divalent cations, and crude oil is withdrawn through atleast one production well from the deposit. The process serves thepurpose of lowering the interfacial tension between oil and water to<0.1 mN/m at deposit temperature. The invention further relates to thepreparation of the mixture and to a concentrate comprising the mixture.

In natural mineral oil deposits, mineral oil is present in the cavitiesof porous reservoir rocks which are sealed toward the surface of theearth by impervious overlying strata. The cavities may be very finecavities, capillaries, pores or the like. Fine pore necks may have, forexample, a diameter of only about 1 μm. As well as mineral oil,including fractions of natural gas, a deposit generally also compriseswater with a greater or lesser salt content.

If a mineral oil deposit has a sufficient autogenous pressure, afterdrilling of the deposit has commenced, mineral oil flows through thewell to the surface of its own accord because of the autogenous pressure(primary mineral oil production). Even if a sufficient autogenouspressure is present at first, however, the autogenous pressure of thedeposit generally declines relatively rapidly in the course ofwithdrawal of mineral oil, and so usually only small amounts of theamount of mineral oil present in the deposit can be produced in thismanner, according to the deposit type.

Therefore, when primary production declines, a known method is to drillfurther wells into the mineral oil-beating formation in addition to thewells which serve for production of the mineral oil, called theproduction wells. Through these so-called injection wells, water isinjected into the deposit in order to maintain the pressure or increaseit again. The injection of the water forces the mineral oil through thecavities in the formation, proceeding gradually from the injection wellin the direction of the production well. This technique is known aswater flooding and is one of the techniques of what is called secondaryoil production. In the case of water flooding, however, there is alwaysthe risk that the mobile water will not flow homogeneously through theformation and in doing so mobilize oil, but will flow from the injectionwell to the production well, particulary along paths with a low flowresistance, without mobilizing oil, while there is only little flow, ifany, through regions in the formation with high flow resistance. This isdiscerned from the fact that the proportion of the water which isproduced via the production well increases ever further. By means ofprimary and secondary production, generally not more than about 30% to35% of the amount of mineral oil present in the deposit can be produced.

A known method is to use techniques for tertiary mineral oil production(also known as “Enhanced Oil Recovery (EOR)”) to enhance the oil yield,if economically viable production is impossible or no longer possible bymeans of primary or secondary mineral oil production. Tertiary mineraloil production includes processes in which suitable chemicals, such assurfactants and/or polymers, are used as auxiliaries for oil production.An overview of tertiary oil production using chemicals can be found, forexample, in the article by D. G. Kessel, Journal of Petroleum Scienceand Engineering, 2 (1989) 81-101.

One of the techniques of tertiary mineral oil production is called“polymer flooding”. Polymer flooding involves injecting an aqueoussolution of a thickening polymer into die mineral oil deposit throughthe injection wells, the viscosity of the aqueous polymer solution beingmatched to the viscosity of the mineral oil. The injection of thepolymer solution, as in the case of water flooding, forces the mineraloil through said cavities in the foundation from the injection wellproceeding in the direction of the production well, and the mineral oilis produced through the production well. By virtue of the polymerformulation having about the same viscosity as the mineral oil, the riskthat the polymer formation will break through to the production wellwith no effect is reduced. Thus, the mineral oil is mobilized much morehomogeneously than when water., which is mobile, is used, and additionalmineral oil can be mobilized in the formation. Details of polymerflooding and polymers suitable for this purpose are disclosed, forexample, in “Petroleum, Enhanced Oil Recovery, Kirk-Othmer, Encyclopediaof Chemical Technology, Online Edition, John Wiley & Sons, 2010”.

Use of hydrophobically associating copolymers for polymer flooding isknown. “Hydrophobically associating copolymers” are understood by thoseskilled in the art to mean water-soluble polymers having lateral orterminal hydrophobic groups, for example relatively long alkyl chains.In an aqueous solution, such hydrophobic groups can associate withthemselves or with other substances having hydrophobic groups. Thisresults in formation of an associative network which causes (additional)thickening action. Details of the use of hydrophobically associatingcopolymers for tertiary mineral oil production are described, forexample, in the review article by Taylor, K. C. and Nasr-El-Din, H. A.in J. Petr. Sci. Eng. 1998, 19, 265-280.

A further form of tertiary mineral oil production is surfactant floodingfor the purpose of producing the oil trapped in the pores b_(y)capillary forces, usually combined with polymer flooding for mobilitycontrol (homogeneous flow through the deposit).

Viscous and capillary forces act on the mineral oil which is trapped inthe pores of the deposit rock toward the end of the secondaryproduction, the ratio of these two forces relative to one anotherdetermining the microscopic oil removal. A dimensionless parameter,called the capillary number, is used to describe the action of theseforces. It is the ratio of the viscosity forces (velocity×viscosity ofthe forcing phase) to the capillary forces (interfacial tension betweenoil and water×wetting of the rock):

$N_{c} = {\frac{\mu \; v}{\sigma \; \cos \; \theta}.}$

In this formula, μ is the viscosity of the fluid mobilizing the mineraloil, v is the Darcy velocity (flow per unit area), σ is the interfacialtension between liquid mobilizing mineral oil and mineral oil, and θ isthe contact angle between mineral oil and the rock (C. Melrose, C. F.Brandner, J. Canadian Petr. Techn. 58, October-December, 1974). Thehigher the capillary number, the greater the mobilization of the oil andhence also the degree of oil removal.

It is known that the capillary number toward the end of secondarymineral oil production is in the region of about 10⁻⁶ and that it isnecessary for the mobilization of additional mineral oil to increase thecapillary number to about 10⁻³ to 10⁻².

For this purpose, it is possible to conduct a particular form of theflooding method—what is known as Winsor type III microemulsion flooding.In Winsor type III microemulsion flooding, the injected surfactants aresupposed to form a Winsor type Ill microemulsion with the water phaseand oil phase present in the deposit. A Winsor type III microemulsion isnot an emulsion with particularly small droplets, but rather athermodynamically stable, liquid mixture of water, oil and surfactants.The three advantages thereof are that

-   -   a very low interfacial tension σ between mineral oil and aqueous        phase is thus achieved,    -   it generally has a very low viscosity and as a result is not        trapped in a porous matrix,    -   it forms with even the smallest energy inputs and can remain        stable over an infinitely long period (conventional emulsions,        in contrast, require high shear forces which predominantly do        not occur in the reservoir, and are merely kinetically        stabilized).

The Winsor type III microemulsion is in equilibrium with excess waterand excess oil. Under these conditions of microemulsion formation, thesurfactants cover the oil-water interface and lower the interfacialtension σ more preferably to values of <10⁻² mN/m (ultra-low interfacialtension). In order to achieve an optimal result, the proportion of themicroemulsion in the water-microemulsion-oil system, for a definedamount of surfactant, should naturally be at a maximum, since thisallows lower interfacial tensions to be achieved.

In this manner, it is possible to alter the form of the oil droplets(the interfacial tension between oil and water is lowered to such adegree that the smallest interface state is no longer flavored and thespherical form is no longer preferred), and they can be forced throughthe capillary openings by the flooding water.

When all oil-water interfaces are covered with surfactant, in thepresence of an excess amount of surfactant, the Winsor type IIImicroemulsion forms. It thus constitutes a reservoir for surfactantswhich cause a very low interfacial tension between oil phase and waterphase. By virtue of the Winsor type III microemulsion having a lowviscosity, it also migrates through the porous deposit rock in theflooding process. Emulsions, in contrast, may remain suspended in theporous matrix and block deposits. If the Winsor type III microemulsionmeets an oil-water interface as yet uncovered with surfactant, thesurfactant from the microemulsion can significantly lower theinterfacial tension of this new interface and lead to mobilization ofthe oil (for example by deformation of the oil droplets).

The oil droplets can subsequently combine to give a continuous oil bank.This has two advantages:

Firstly, as the continuous oil bank advances through new porous rock,the oil droplets present there can coalesce with the bank.

Moreover, the combination of the oil droplets to give an oil banksignificantly reduces the oil-water interface and hence surfactant nolonger required is released again. Thereafter, the surfactant released,as described above, can mobilize oil droplets remaining in theformation.

Winsor type III microemulsion flooding is consequently an exceptionallyefficient process, and requires much less surfactant compared to anemulsion flooding process. In microemulsion flooding, the surfactantsare typically optionally injected together with cosolvents and/or basicsalts (optionally in the presence of chelating agents). Subsequently, asolution of thickening polymer is injected for mobility control. Afurther variant is the injection of a mixture of thickening polymer andsurfactants, cosolvents and or basic salts (optionally with chelatingagent), and then a solution of thickening polymer for mobility control.These solutions should generally be clear in order to prevent blockagesof the reservoir.

The use parameters, for example type, concentration and mixing ratio ofthe surfactants used relative to one another, are adjusted by the personskilled in the art to the conditions prevailing in a given oil formation(for example temperature and salt content).

PRIOR ART

U.S. Pat. No. 4,457,373 A1 describes the use of water-oil emulsions ofanionic surfactants of the R—(OCH₂CH₂)_(n)—OCH₂COOM type, which arebased on an alkyl radical R having 6 to 20 carbon atoms or an alkylatedaromatic radical in which the total number of carbon atoms in the alkylradicals is 3 to 28, in tertiary mineral oil production. In the repeatunits, n is a number from 1 to 30. The surfactants are prepared via areaction of the corresponding alkoxylates with chloroacetic acid sodiumsalt and sodium hydroxide or aqueous sodium hydroxide solution. Thecarboxymethylation level may range from 10% to 100% (preferably90-100%). The examples show only the use of water-oil emulsionscomprising carboxymethylated r_(i)onylphenol ethoxylate sodium saltwith, for example, n=6 (carboxymethylation level 80%) orcarboxymethylated fatty alcohol ethoxylate sodium salts with, forexample, R=C12C14 and n=4.5 (carboxymethylation level 94%) against crudeoil in salt water at temperatures of 46 to 85° C. The surfactantconcentration used (>5 percent by weight) was very high in the floodingtests, which were conducted at ≤55° C. A polymer (polysaccharides) wasused in the flooding tests.

U.S. Pat. No. 4,485,873 A1 describes the use of anionic surfactants ofthe R—(OCH₂CH₂)_(n)—OCH₂COOM type, which are based on an alkyl radical Rhaving 4 to 20 carbon atoms or an alkylated aromatic radical in whichthe total number of carbon atoms in the alkyl radicals is 1 to 28, intertiary mineral oil production. In the repeat units, n is a number from1 to 30. The surfactants are prepared via a reaction of thecorresponding alkoxylates with chloroacetic acid sodium salt and sodiumhydroxide or aqueous sodium hydroxide solution. The carboxymethylationlevel may range from 10% to 100% (preferably 50-100%). The examples showonly the use of carboxymethylated nonylphenaethoxylate sodium saltswith, for example, n=5.5 (carboxymethylation level 70%) orcarboxymethylated fatty alcohol ethoxylate sodium salts with, forexample, R=C12C14 and n=4.4 (carboxymethylation level 65%) against modeloil in salt water at temperatures of 37 to 74° C. The surfactantconcentration used (>5 percent by weight) was very high in the floodingtests, which were conducted at ≤60° C. The polymer used in the floodingtests was hydroxyethyl cellulose.

U.S. Pat. No. 4,542,790 A1 describes the use of anionic surfactants ofthe R—(OCH₂CH₂)_(n)—OCH₂COOM type, which are based on an alkyl radical Rhaving 4 to 20 carbon atoms or an alkylated aromatic radical in whichthe total number of carbon atoms in the alkyl radicals is 1 to 28, intertiary mineral oil production. In the repeat units, n is a number from1 to 30. The surfactants are prepared via a reaction of thecorresponding alkoxylates with chloroacetic acid sodium salt and sodiumhydroxide or aqueous sodium hydroxide solution. The carboxymethylationlevel may range from 10% to 100%. The examples show the use ofcarboxymethylated nonylphenol ethoxylate sodium salts with, for example,n=5.3 (carboxymethylation level 76%) or carboxymethylated C12C14 fattyalcohol ethoxylate sodium salts against low-viscosity crude oil (10 mPasat 20° C.) in salt water at temperatures of 46 to 85° C. The surfactantconcentration used (2 percent by weight) was relatively high in theflooding tests, which were conducted at ≤60° C.

U.S. Pat. No. 4,811,788 A1 discloses the use of R—(OCH₂CH₂)_(n)—OCH₂COOMwhich are based on the alkyl radical 2-hexyldecyl (derived from C16Guerbet alcohol) and in which ii is the number 0 or 1 in tertiarymineral oil production.

EP 0207312 B1 describes the use of anionic surfactants of theR—(OCH₂C(CH₃)H)_(m)(OCH_(n)CH₂)_(n)—OCH₂COOM type, which are based on analkyl radical R having 6 to 20 carbon atoms or an alkylated aromaticradical in which the total number of carbon atoms in the alkyl radicalsis 5 to 40, in a blend with a more hydrophobic surfactant in tertiarymineral oil production. In the repeat units, m is a number from 1 to 20and n is a number from 3 to 100. The surfactants are prepared via areaction of the corresponding alkoxylates with chloroacetic acid sodiumsalt and sodium hydroxide or aqueous sodium hydroxide solution. Thecarboxymethylation level may range from 10% to 100%. The examples showthe use of carboxymethylated dinonylphenol block propoxy ethoxylatesodium salt with m=3 and n=12 (carboxymethylation level 75%) togetherwith alkylbenzenesulfouate or alkanesulfonate against model oil inseawater at temperatures of 20° C. or 90° C. Oil recovery at 90° C. incore flooding tests gave poorer values than at 20° C., and thesurfactant concentration used (4 percent by weight) was very high.

WO 2009/100298 A1 describes the use of anionic surfactants of theR¹—O—(CH₂C(CH₃)HO)_(m)(CH₂CH₂O)_(n)—XY⁻ M⁺ type, which are based on abranched alkyl radical R¹ having 10 to 24 carbon atoms and a branchinglevel of 0.7 to 2.5, in tertiary mineral oil production. Y⁻ may be acarboxylate group inter alia. In the examples of the alkyl ethercarboxylates, R¹ is always a branched alkyl radical having 16 to 17carbon atoms and X is always a CH₂ group. For the repeat units, exampleswith m=0 and n=9 and m=7 and n=2 and m=3.3 and n=6 are detailed. Thesurfactants are prepared via a reaction of the corresponding alkoxylateswith chloroacetic acid sodium salt and aqueous sodium hydroxidesolution. The carboxymethylation level is disclosed as 93% for theexample with m=7 and n=2. In the examples, the alkyl ether carboxylatesare tested as sole surfactants (0.2 percent by weight) in seawater at72° C. against crude oil. The interfacial tensions attained were alwaysabove 0.1 mN/m.

WO 09124922 A1 describes the use of anionic surfactants of theR¹—O—(CH₂C(R²)HO)_(n′)(CH₂CH₂O)_(m″)—R⁵-COOM type, which are based on abranched saturated alkyl radical R¹ having 17 carbon atoms and abranching level of 2.8 to 3.7, in tertiary mineral oil production. R² isa hydrocarbyl radical having 1 to 10 carbon atoms. R⁵ is a divalenthydrocarbyl radical having 1 to 12 carbon atoms. In addition, n″ is anumber from 0 to 15 and m″ is a number from 1 to 20. These anionicsurfactants can be obtained inter alia by oxidation of correspondingalkoxylates, with conversion of a terminal —CH₂CH₂OH group to a terminal—CH₂CO₂M group.

WO 11110502 A1 describes the use of anionic surfactants of theR¹—O—(CH₂C(CH₃)HO)_(m)(CH₂CH₂O)_(n)—XY M⁺ type, which are based on alinear saturated or unsaturated alkyl radical R¹ having 16 to 18 carbonatoms, in tertiary mineral oil production. Y⁻ may be a carboxylate groupinter alia, and X may be an alkyl or alkylene group having up to 10carbon atoms inter alia. In addition, m is a number from 0 to 99 andpreferably 3 to 20, and n is a number from 0 to 99. These anionicsurfactants can be obtained inter alia by reaction of appropriatealkoxylates with chloroacetic acid sodium salt.

WO 2012/027757 A1 claims surfactants of theR¹—O—(CH₂C(R²)HO)_(n)(CH(R³)₂-COOM type and the use thereof in tertiarymineral oil production. R¹ represents alkyl radicals or optionallysubstituted cycloalkyl or optionally substituted aryl radicals eachhaving 8 to 150 carbon atoms. R² or R³ may be H or alkyl radicals having1 to 6 carbon atoms. The value n is a number from 2 to 210 and z is anumber from 1-6. The only examples are surfactant mixtures at leastcomprising a sulfonate-containing surfactant (e.g. internalolefinsulfonates or alkylbenzenesulfonates) and an alkyl ethercarboxylate in which R¹ is a branched saturated alkyl radical having 24to 32 carbon atoms and derives from Guerbet alcohols having only onebranch (in the 2 position). Said alkyl ether carboxylates have at least25 repeat units in which R² is CH₃, and at least 10 repeat units inwhich R² is H, and so n is at least a number greater than 39. In all theexamples, R³ is H and z is the number 1. The surfactant mixtures containat least 0.5 percent by weight of surfactant and are tested attemperatures of 30 to 105° C. against crude oils.

WO 2013/159027 A1 claims surfactants of the R¹—O—(CH₂C(R²)HO)_(n)—X typeand the use thereof in tertiary mineral oil production. R¹ representsalkyl radicals each having 8 to 20 carbon atoms, or optionallysubstituted cycloalkyl or optionally substituted aryl radicals, R² maybe H or CH₃. The value n is a number from 25 to 115. X is SO₃M, SO₃H,CH₂CO₂M or CH₂CO₂H (M⁺ is a cation). Additionally disclosed arestructures of the R¹—O—(CH₂C(CH₃)HO)_(x)—(CH₂CH₂O)_(y)—X type, where xis a number from 35 to 50 and y is a number from 5 to 35. One example isthe surfactant C₁₈H₃₅—O—(CH₂C(CH₃)HO)₄₅—(CH₂CH₂O)₃₀—CH₂CO₂M (C₁₈H₃₅ isoleyl) in a blend with an internal C₁₉—C₂₈ olefinsulfonate and phenyldiethylene glycol. The surfactant mixtures contain at least 1.0 percentby weight of surfactant and are tested at temperatures of 100° C. andtotal salinity 32500 ppm in the presence of the base sodium metaborateagainst crude oils.

DE 2418444 A1 discloses the preparation of alkyl ether carboxylic acidsby reaction of alcohols or alcohol ethoxylates with chloroacetic acidsodium salt and sodium hydroxide or sodium hydroxide solution at 20-80°C. with subsequent addition of sulfuric acid and phase separation at 90°C.

EP 0106018 A1 discloses the preparation of carboxymethylated alcohols,alkyl ethoxylates or alkylphenol ethoxylates by reaction of alcohols,alkyl ethoxylates or alkylphenol ethoxylates with chloroacetic acid andsodium hydroxide solution (double the molar amount in relation tochloroacetic acid) at 70-95° C. and under reduced pressure, with theproviso that 0.3% to 1.25% water is present in the reaction mixture.

US 2010/0081716 A1 discloses the preparation of carboxymethylated alkylalkoxylate. This involves base-catalyzed alkoxylation of alcohol,neutralization with a hydroxycarboxylic acid or a dicarboxylic acid or atricarboxylic acid, and then reaction with chloroacetic acid orchloroacetic salt and alkali metal hydroxide.

U.S. Pat. No. 8,304,575 B2 discloses the prepatation ofcarboxymethylated alkyl alkoxylate. This involves base-catalyzedalkoxylation of alcohol, neutralization with a hydroxycarboxylic acid ora dicarboxylic acid or a tricarboxylic acid, and then conversion withsimultaneous addition of aqueous solution of chloroacetic acid orchloroacetic salt and of an aqueous alkali metal hydroxide solution at50-100° C. and under a reduced pressure of 0.0067 to 266 mbar.

EP 1 061 064 B1 describes a process for preparing ether carboxylic acidshaving a low residual alcohol content.

S. Chen et al., Int. J. Oil and Coal Technology, vol. 7, no. 1, 2014,pages 52-66 describe the synthesis and suitability of alcohol ethercarboxylates for alkali-surfactant polymer flooding at very lowtemperatures of <30° C.

OBJECT OF THE INVENTION

There is a need for greater oil recovery from deposits having salinedeposit water and having deposit temperatures of 55° C. to 150° C. withsurfactants or surfactant formulations having the following properties:

-   -   hydrolysis stability;    -   salt tolerance (rater solubility even in the presence of many        monovalent ions, but also polyvalent cations: for example saline        water having more than 100 ppm of divalent cations such as Ca²⁺        and/or Mg²⁺);    -   low use concentrations (<0.5 percent by weight) in order to keep        costs and material consumption low with a view to        sustainability;    -   simple injection into the porous formation (virtually complete        dissolution in a clear solution at reservoir temperature);    -   low interfacial tensions at deposit temperature with respect to        crude oil (<0.1 mN/m, more preferably <0.01 mN/m), even when        using only one surfactant (or two very similar surfactants which        differ only in a few aspects—for example small differences in        the alkoxylation level). This is found to be difficult since the        oil-water interface is caused to oscillate with increasing        temperature (excursion because of Brownian molecular motion) and        increases in size as a result. There is a need for an efficient        surfactant in order to adequately cover the interface and        nevertheless lower the interfacial tension to a low value (<0.1        mN/m);    -   low adsorption at the rock surface;    -   in some cases, base-free formulations, since use of alkali is        impossible because of the presence of polyvalent cations (leads        to precipitation and hence loss of alkali) or the pores and        hence the deposit are blocked because of scale formation;    -   simple production process, in order to keep the costs of the        surfactant low;    -   supply form as surfactant concentrate which may be liquid at at        least 20° C. (this would obviate the need for melting of the        concentrate or constant heating on site), and should preferably        have a viscosity of <1500 mPas at 40° C. and 200 Hz (this would        allow simple pumping) and a high active content (this would keep        the transport costs and the energy consumption resulting from        transport low; added water and particular cosolvents do lower        the melting point and viscosity of the concentrate but also have        to be transported, which consumes energy; in addition,        relatively large storage vessels would be required on site,        which increases infrastructure costs or is not very viable in        the field of offshore applications, since it takes up valuable        space);    -   it should not have any environmentally harmful properties        (alkylphenol ethoxylates or their degradation products are known        to be able to act as endocrine disruptors. If they are used as        raw material for other surfactant structures, it should be        ensured that they are converted completely).

In this context, particularly the attainment of low interfacial tensionsof <0.1 mN/m and especially <0.01 mN/m at temperatures of >55° C. isdifficult (especially when it is not possible to use a base such asalkali metal hydroxide or sodium carbonate because of the waterhardness, since it could otherwise lead to formation of scale).

With regard to the head group in surfactants, olefinsulfonates,paraffinsulfonates or alkylarylsulfonates are hydrolysis-stable underthe conditions outlined above, but have little or barely any salttolerance as an individual surfactant. Thus, an internal C20C24olefinsulfonate alone would be insoluble in formation water with, forexample, salt content 10% and 2000 ppm of divalent cations andtemperatures of up to 150° C.

Alkyl ether sulfates are not hydrolysis-stable above 55° C. unless abasic pH of about 10-11 is maintained. However, this is unachievable inmany cases since no alkali can be used because of the water hardness, orthe reservoir rock reacts with the base and, as a result, the pH changesin the direction of neutral pH values.

Alkyl ether sulfonates often combine hydrolysis stability and salttolerance, but their preparation is complex (multistage syntheses or useof reagents that are difficult to handle) and they are usually veryexpensive.

An alternative approach is that of using the class of thecarboxymethylated alkyl alkoxylates, which can be obtained by reactionof alkyl alkoxylate with, for example, chloroacetic acid sodium salt.They are hydrolysis-stable and may be salt-tolerant. However, themixtures described in the prior art either require high surfactant useconcentrations or are based on environmentally harmful raw materials(alkylphenol alkoxylates) or have to be used in combination with otherchemically different stufactants (i.e. surfactants which do not serve asstarting raw material for the alkyl ether carboxylate: for exampleorganic sultanates such as alkylbenzenesulfonates or olefinsulfonates)to achieve very low interfacial tensions.

The flooding process is an industrial scale process. Although thechemicals used are typically used only as dilute solutions, the volumesinjected per day are high and the injection is typically continued overmonths and up to several years. The chemical requirement for an averageoilfield may quite possibly be 5000 to 10 000 t of polymer per annum.For an economically viable process, therefore, a very high efficiency,i.e. effect per unit volume, is of great significance. Even a slightimprovement in efficiency can lead to a significant improvement ineconomic viability. Consequently, lowering of the interfacial tensionbetween oil and water to <0.1 mN/m with a low use concentration ofsurfactant is desirable (total amount of all surfactants should ideallyaccount for <0.5 percent by weight of the aqueous surfactant-containingsolution injected. The injected aqueous surfactant-containing solutionis understood to mean what is called the injected surfactant slug. Thesurfactant slug fills a portion of the pore volume and may, as well asthe surfactant, optionally comprise further additives, for example athickening polymer. The desired portion of the pore volume may, forexample, be between 2% and 60%, preferably between 3% and 25%).

There is therefore a need for surfactant mixtures comprisingcarboxymethylated alkyl alkoxylates and the starting material thereof,which, in oil production under the abovementioned conditions, do nothave at least some of the disadvantages detailed in the prior art and/orfulfill a maximum number of the abovementioned properties.

GENERAL DESCRIPTION OF THE INVENTION

For the achievement of the above object, it has therefore been foundthat, surprisingly, the demands are met by a method for producingmineral oil from underground mineral oil deposits (optionally by meansof Winsor type III microemulsion flooding), in which an aqueous salinesurfactant formulation comprising a surfactant mixture, for the purposeof lowering the interfacial tension between oil and water to <0.1 mN/mat deposit temperature, is injected through at least one injection wellinto a mineral oil deposit and crude oil is withdrawn through at leastone production well from the deposit, wherein

-   -   a) the mineral oil deposit has a deposit temperature of 55° C.        to 150° C., a crude oil having more than 20° API and a deposit        water having more than 100 ppm of divalent cations;    -   and    -   b) the surfactant mixture comprises at least one anionic        surfactant (A) of the general formula (I)

R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)₂—CH₂CO₂M   (I)

-   -   -   and at least one nonionic surfactant (B) of the general            formula (II)

R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H   (II),

-   -   -   where a molar ratio of anionic surfactant (A) to nonionic            surfactant (B) of 51:49 to 92:8 is present in the surfactant            mixture on injection and the nonionic surtactant (B) serves            as starting material for the anionic surfactant (A),

    -   where

    -   R¹ is a primary linear or branched, saturated or unsaturated,        aliphatic hydrocarbyl radical having 10 to 36 carbon atoms;

    -   R² is a linear saturated aliphatic hydrocarbyl radical having 2        to 14 carbon atoms;

    -   M is H, Na, K or NH₄;

    -   x is a number from 0 to 10;

    -   y is a timber from 0 to 50;

    -   z is a number from 1 to 35;

where the sum total of x+y+z is a number from 3 to 80 and the alkoxylategroups may be arranged m random distribution, in alternation or inblocks;

-   -   and    -   c) the concentration of all the surfactants together is 0.05% to        0.49% by weight, based on the total amount of the aqueous saline        surfactant formulation.

The aqueous saline surfactant formulation is understood to mean asurfactant mixture which is dissolved in saline water (for exampleduring the injection operation). The saline water may, inter alia, beriver water, seawater, water from an aquifer close to the deposit,so-called injection water, deposit water, so-called production waterwhich is being reinjected again, or mixtures of the above-describedwaters. However, the saline water may also be that which has beenobtained from a more saline water: for example partial desalination,depletion of the polyvalent cations or by dilution with fresh water ordrinking water. The surfactant mixture can preferably be provided as aconcentrate which, as a result of the preparation, may also comprisesalt. This is detailed further in the paragraphs which follow.

In the context of this invention, alkyl ether alcohol is understood tomean the alkyl alkoxylates or polyethers which arise from the reactionof alcohols with alkylene oxides: i.e. compounds of theR¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)₂—H type. Thesenonionic compounds may be alkyl ether alcohols or alkenyl etheralcohols. Since the compounds are preferably alkyl ether alcohols, theyare referred to hereinafter simply as alkyl ether alcohols. Thesituation is similar for the group of the alkyl ether carboxylatesR¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)-(CH₂CH₂O)_(z)—CH₂CO₂M. These arealkenyl ether carboxylates or preferably alkyl ether carboxylates. Thealkyl ether carboxylatelalkyl ether alcohol mixture is preferablyprepared by carboxymethylation of the corresponding alkyl alkoxylateusing chloroacetic salt or chloroacetic acid, in each case in thepresence of an alkali metal hydroxide.

Therefore, the term “starting material” in the context of the presentinvention means that, for every surfactant of the formula (I) in thesurfactant mixture, there is a surfactant of the formula (II) having thesame definition of the variables R¹, R², x, y, z. This canadvantageously be achieved by virtue of surfactants of the formula (II)serving as reactant for the preparation of the products of the formula(I). Accordingly, the methods of the invention for production of mineraloil preferably also comprise upstream method steps for the inventivepreparation of the surfactant mixtures.

Accordingly the present invention also relates to methods for productionof mineral oil, wherein the surfactant mixture of anionic surfactant (A)of the general formula (I) and nonionic surfactant (B) of the generalformula (II) is obtained by at least one of the following reactionconditions:

-   -   the anionic surfactant (A) of the general formula (I) is        prepared in a reactor by reacting the nonionic surfactant (B) of        the general formula (II), preferably while stirring, with        chloroacetic acid or chloroacetic acid sodium salt in the        presence of alkali metal hydroxide or aqueous alkali metal        hydroxide, with removal of water of reaction such that the water        content in the reactor is kept at a value of 0.2% to 1.7% during        the carboxymethylation by applying reduced pressure and/or by        passing nitrogen through;    -   aqueous NaOH (preferably 40-80% strength) as alkali metal        hydroxide and aqueous chloroacetic acid (preferably 75-85%        strength) are used in a carboxymethylation, using NaOH in        relation to the chloroacetic acid in a ratio of 2 eq:1 eq to 2.2        eq:1 eq;        -   and        -   the nonionic surfactant (B) is prepared either via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH or via an            alkoxylation using a double metal cyanide catalyst, and the            alkoxylation catalyst is not neutralized and is not removed            after the alkoxylation has ended;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in the reactor in the carboxymethylation            and the sodium hydroxide and chloroacetic acid are metered            in in parallel at a temperature of 60-110° C. over a period            of 1-7 h, the metered addition over the entire period being            effected continuously or in equal portions every hour, and            the stoichiometric ratio of nonionic surfactant (B) of the            general formula (II) to the chloroacetic acid being 1 eq:1            eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1 eq:1.5 eq);        -   and        -   the water content in the reactor is kept predominantly at an            average value of 0.2% to 1.7% during the carboxymethylation            by applying reduced pressure and/or by passing nitrogen            through; and/or    -   NaOH as alkali metal hydroxide and chloroacetic acid sodium salt        are used in the carboxymethylation, using NaOH in relation to        the chloroacetic acid sodium salt in a ratio of 1 eq:1 eq to 1        eq:1.9 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH and is            preferably used in unneutralized form in the            carboxymethylation;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in a reactor in the carboxymethylation            together with NaOH or aqueous NaOH (preferably 40-80%            strength), where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to NaOH is 1 eq:1            eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1 eq:1.35 eq), a            temperature of 60-110° C. is set, and the nonionic            surfactant (B) of the general formula (II) is converted to            the corresponding sodium salt            R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na by            applying reduced pressure and/or passing nitrogen through            and, at a temperature of 60-110° C., the chloroacetic acid            sodium salt is metered in completely or preferably over a            period of 4-12 h, where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to the            chloroacetic acid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq            (preferably 1 eq:1 eq to 1 eq:1.5 eq) and where the metered            addition over the entire period is effected continuously or            in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;    -   solid NaOH as alkali metal hydoxide and chloroacetic acid sodium        salt are used in the carboxymethylation, using NaOH in relation        to the chloroacetic acid sodium salt in a ratio of 1 eq:1 eq to        1.1 eq:1 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation using KOH or NaOH or CsOH and            then neutralized with acetic acid and is used in the            carboxymethylation together with initially 0.5-1.5% water;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in a reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70° C. over a period of 4-12 h, the            metered addition being effected continuously over the entire            period or in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;    -   Solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH or,        in the case of a basic alkoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—K or the        sum total in the case of a basic alkoxylate of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na or, in        the case of a basic allcoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Cs in        relation to the chloroacetic acid sodium salt in a ratio of 1.1        eq:1 eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1.1 eq:1 eq),        where the ratio of nonionic surfactant (B) of the general        formula (II):NaOH is from 1 eq:1 eq to 1 eq:1.5 eq;        -   and        -   the nonionic surfactant (B) is prepared via a base-catalyzed            alkoxylation using KOH or NaOH or CsOH or a mixture of NaOH            and KOH, an is used in the carboxymethylation either in            neutralized and filtered (i.e. salt-free) form or in the            form of an unneutralized basic alkoxylate (preferably <5 mol            % of base as alkoxylation catalyst);        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            were the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1. eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq, more preferably 1 eq:1 eq to 1 eq:135 eq), and            the sodium hydroxide is metered in at a temperature of            20-70° C. over a period of 4-12 h, the metered addition            being effected continuously over the entire period or in            equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;

solid NaOH as alkali metal hydroxide and chloroacetic acid sodium saltare used in the carboxymethylation, using NaOH in relation to thechloroacetic acid sodium salt in a ratio of 1 eq:1 eq to 1.1 eq:1 eq;

-   -   -   and        -   the nonionic surfactant (B) has been prepared via an            alkoxylation using double metal cyanide catalysis;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70′C over a period of 4-12 h, the addition            being effected continuously over the entire period or in            equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% dining the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through.

A further aspect of the present invention relates to a concentratecomposed of anionic surfactant (A) of the general formula (I) andnonionic surfactant (B) of the general formula (II), comprising 20% byweight to 70% by weight of the surfactant mixture, 10% by weight to 40%by weight of water and 10% by weight to 40% by weight of a cosolvent,based on the total amount of the concentrate, where preferably

-   -   -   a) the cosolvent is selected from the group of the aliphatic            alcohols having 3 to 8 carbon atoms or from the group of the            alkyl monoethylene glycols, the alkyl diethylene glycols or            the alkyl triethylene glycols, where the alkyl radical is an            aliphatic hydrocarbyl radical having 3 to 6 carbon atoms;        -   and/or        -   b) the concentrate is free-flowing at 20° C. and has a            viscosity at 40° C. of <1500 mPas at 200 Hz, where a molar            ratio of anionic surfactant (A) to nonionic surfactant (B)            cif 51:49 to 92:8, preferably of 70:30 to 92:8, is present            in the concentrate.

The concentrate may comprise, for example, as well as the alkyl ethercarboxylate/alkyl alkoxylate mixture, also alkali metal chloride anddiglycolic acid dialkali metal salt. Optionally, it also compriseschloroacetic acid alkali metal salt, glycolic acid alkali metal salt,water and/or a cosolvent. The cosolvent is, for example, butyl ethyleneglycol, butyl diethylene glycol or butyl triethylene glycol.

The concentrate preferably comprises 0.5% to 15% by weight of a mixturecomprising NaCl and diglycolic acid disodium salt, where NaCl is presentin excess relative to diglycolic acid disodium salt.

Further preferably, the concentrate comprises butyl diethylene glycol ascosolvent.

A further aspect of the present invention relates to a productionprocess for the surfactant mixture.

Accordingly, the present invention also relates to a method forproducing a surfactant mixture of anionic surfactant (A) of the generalformula (I) and nonionic surfactant (B) of the general formula (II) asdescribed hereinafter, wherein a molar ratio of anionic surfactant (A)to nonionic surfactant (B) of 51:49 to 92:8 (preferably 70:30 to 92:8)is present in the surfactant mixture at the end of the reaction.

More particularly, the production may be effected as follows:

-   -   The anionic surfactant (A) of the general formula (I) is        prepared by reacting the nonionic surfactant (B) of the general        formula (II), preferably while stirring, with chloroacetic acid        or chloroacetic acid sodium salt in the presence of alkali metal        hydroxide or aqueous alkali metal hydroxide, with removal of        water of reaction such that the water content in the reactor is        kept at a value of 0.2% to 1.7% during the carboxymethylation by        applying reduced pressure and/or by passing nitrogen through;        and/or    -   Aqueous NaOH (preferably 40-80% strength) as alkali metal        hydroxide and aqueous chloroacetic acid (preferably 75-85%        strength) are used in the carboxymethylation, using NaOH in        relation to the chloroacetic acid in a ratio of 2 eq:1 eq to 2.2        eq:1 eq;        -   and        -   the nonionic surfactant (B) is prepared either via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH or via an            alkoxylation using a double metal cyanide catalyst, and the            alkoxylation catalyst is not neutralized and is not removed            after the alkoxylation has ended;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in the reactor in the carboxymethylation            and the sodium hydroxide and chloroacetic acid are metered            in in parallel at a temperature of 60-110° C. over a period            of 1-7 h, the metered addition over the entire period being            effected continuously or in equal portions every hour, and            the stoichiometric ratio of nonionic surfactant (B) of the            general formula (II) to the chloroacetic acid being 1 eq:1            eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to1 eq:1.5 eq);        -   and        -   the water content in the reactor is kept predominantly at an            average value of 0.2% to 1.7% during the carboxymethylation            by applying reduced pressure and/or by passing nitrogen            through; and/or    -   NaOH as alkali metal hydroxide and chloroacetic acid sodium salt        are used in the carboxymethylation, using NaOH in relation to        the chloroacetic acid sodium salt in a ratio of 1 eq:1 eq to 1        eq:1.9 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH and is            preferably used in unneutralized form in the            carboxymethylation;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in the reactor in the carboxymethylation            together with NaOH or aqueous NaOH (preferably 40-80%            strength), where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to NaOH is 1 eq:1            eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1 eq:1.35 eq), a            temperature of 60-110° C. is set, and the nonionic            surfactant (B) of the general formula (II) is converted to            the corresponding sodium salt            R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na by            applying reduced pressure and/or passing nitrogen through            and, at a temperature of 60-110° C., the chloroacetic acid            sodium salt is metered in completely or preferably over a            period of 4-12 h, where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to the            chloroacetic acid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq            (preferably 1 eq:1 eq to 1 eq:1.5 eq) and where the metered            addition over the entire period is effected continuously or            in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through; and/or    -   solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH in        relation to the chloroacetic acid sodium salt in a ratio of 1        eq:1 eq to 1.1 eq:1 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation using KOH or NaOH or CsOH and            then neutralized with acetic acid and is used in the            carboxymethylation together with initially 0.5-1.5% water;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70° C. over a period of 4-12 h, the            metered addition being effected continuously over the entire            period or in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through; and/or    -   Solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH or,        in the case of a basic alkoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—K or the        sum total in the case of a basic alkoxylate of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na or, in        the case of a basic alkoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Cs in        relation to the chloroacetic acid sodium salt in a ratio of 1.1        eq:1 eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1.1 eq:1 eq),        where the ratio of nonionic surfactant (B) of the general        formula (II):NaOH is from 1 eq:1 eq to 1 eq:1.5 eq;        -   and        -   the nonionic surfactant (B) is prepared via a base-catalyzed            alkoxylation using KOH or NaOH or CsOH or a mixture of NaOH            and KOH, and is used in the carboxymethylation either in            neutralized and filtered (i.e. salt-free) form or in the            form of an unneutralized basic alkoxylate (preferably <5 mol            % of base as alkoxylation catalyst);        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq, more preferably 1 eq:1 eq to 1 eq:1.35 eq), and            the sodium hydroxide is metered in at a temperature of            20-70° C. over a period of 4-12 h, the metered addition            being effected continuously over the entire period or in            equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through; and/or    -   solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH in        relation to the chloroacetic acid sodium salt in a ratio of 1        eq:1 eq to 1.1 eq:1 eq;        -   and the nonionic surfactant (B) has been prepared via an            alkoxylation using double metal cyanide catalysis;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70° C. over a period of 4-12 h, the            metered addition being effected continuously over the entire            period or in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through.

Accordingly, a further aspect of the present invention is a method forproducing a surfactant mixture by carboxymethylation comprising at leastone anionic surfactant (A) of the general formula (I)

R¹ 13 O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M   (I)

-   -   -   -   and at least one nonionic surfactant (B) of the general                formula (II)

R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H   (II),

-   -   -   where a molar ratio of anionic surfactant (A) to nonionic            surfactant (B) of 51:49 to 92:8 (preferably 60:40 to 92:8,            more preferably 70:30 to 92:8, more preferably 70:30 to            89:11) is present in the surfactant mixture on injection and            the nonionic surfactant (B) serves as starting material for            the anionic surfactant (A),        -   where        -   R¹ is a primary linear or branched, saturated or            unsaturated, aliphatic hydrocarbyl radical having 10 to 36            carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 2 to 14 carbon atoms; and        -   M is H, Na, K or NH₄; and        -   x is a number from 0 to 10; and        -   y is a number from 0 to 50; and        -   z is a number from 1 to 35;        -   where the sum total of x+y+z is a number from 3 to 80 and            the x+y+z alkoxylate groups may be arranged in random            distribution, in alternation or in blocks; and        -   where the sum total of x+y is a number >0 if R¹ is a primary            linear, saturated or unsaturated, aliphatic hydrocarbyl            radical having 10 to 36 carbon atoms, wherein at least one            of the following reaction conditions is used:

    -   the anionic surfactant (A) of the general formula (I) is        prepared in a reactor by reacting the nonionic surfactant (B) of        the general formula (II), preferably while stirring, with        chloroacetic acid or chloroacetic acid sodium salt in the        presence of alkali metal hydroxide or aqueous alkali metal        hydroxide, with removal of water of reaction such that the water        content in the reactor is kept at a value of 0.2% to 1.7% during        the carboxymethylation by applying reduced pressure and/or by        passing nitrogen through;

    -   aqueous NaOH (preferably 40-80% strength) as alkali metal        hydroxide and aqueous chloroacetic acid (preferably 75-85%        strength) are used in a carboxymethylation, using NaOH in        relation to the chloroacetic acid in a ratio of 2 eq:1 eq to 2.2        eq:1 eq;        -   and        -   the nonionic surfactant (B) is prepared either via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH or via an            alkoxylation using a double metal cyanide catalyst, and the            alkoxylation catalyst is not neutralized and is not removed            after the alkoxylation has ended;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in the reactor in the carboxymethylation            and the sodium hydroxide and chloroacetic acid are metered            in in parallel at a temperature of 60-110°C. over a period            of 1-7 h, the metered addition over the entire period being            effected continuously or in equal portions every hour, and            the stoichiometric ratio of nonionic surfactant (B) of the            general formula (II) to the chloroacetic acid being 1 eq:1            eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1 eq:1.5 eq);        -   and        -   the water content in the reactor is kept predominantly at an            average value of 0.2% to 1.7% during the carboxymethylation            by applying reduced pressure and/or by passing nitrogen            through;

    -   NaOH as alkali metal hydroxide and chloroacetic acid sodium salt        are used in the carboxymethylation, using NaOH in relation to        the chloroacetic acid sodium salt in a ratio of 1 eq:1 eq to 1        eq:1.9 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH and is            preferably used in unneutralized form in the            carboxymethylation;        -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in a reactor in the carboxymethylation            together with NaOH or aqueous NaOH (preferably 40-80%            strength), where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to NaOH is 1 eq:1            eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1 eq:1.35 eq), a            temperature of 60-110° C. is set, and the nonionic            surfactant (B) of the general formula (II) is converted to            the corresponding sodium salt            R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na by            applying reduced pressure and/or passing nitrogen through            and, at a temperature of 60-110° C., the chloroacetic acid            sodium salt is metered in completely or preferably over a            period of 4-12 h, where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to the            chloroacetic acid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq            (preferably 1 eq:1 eq to 1 eq:1.5 eq) and where the metered            addition over the entire period is effected continuously or            in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;

    -   solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH in        relation to the chloroacetic acid sodium salt in a ratio of 1        eq:1 eq to 1.1 eq:1 eq;        -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation using KOH or NaOH or CsOH and            then neutralized with acetic acid and is used in the            carboxymethylation together with initially 0.5-1.5% water;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the genera formula(II) are initially            charged together in a reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1eq:1 eq to 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70° C. over a period of 4-12 h, the            metered addition being effected continuously over the entire            period or in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;

    -   Solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH or,        in the case of a basic alkoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—K or the        sum total in the case of a basic alkoxylate of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na or, in        the case of a basic alkoxylate, the sum total of NaOH and        R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Cs in        relation to the chloroacetic acid sodium salt in a ratio of 1.1        eq:1 eq to 1 eq:15 eq (preferably 1 eq:1 eq to 1.1 eq:1 eq),        where the ratio of nonionic surfactant (B) of the general        formula (II):NaOH is from 1 eq:1 eq to 1 eq:1.5 eq;        -   and        -   the nonionic surfactant (B) is prepared via a base-catalyzed            alkoxylation using KOH or NaOH or CsOH or a mixture of NaOH            and KOH, and is used in the carboxymethylation either in            neutralized and filtered (i.e. salt-free) form or in the            form of an unneutralized basic alkoxylate (preferably <5 mol            % of base as alkoxylation catalyst);        -   and chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq, more preferably 1 eq:1 eq to 1 eq:1.35 eq), and            the sodium hydroxide is metered in at a temperature of            20-70° C. over a period of 4-12 h, the metered addition            being effected continuously over the entire period or in            equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through;

    -   solid NaOH as alkali metal hydroxide and chloroacetic acid        sodium salt are used in the carboxymethylation, using NaOH in        relation to the chloroacetic acid sodium salt in a ratio of 1        eq:1 eq to 1.1 eq:1 eq;        -   and        -   the nonionic surfactant (B) has been prepared via an            alkoxylation using double metal cyanide catalysis;        -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq t© 1            eq:1.5 eq), and the sodium hydroxide is metered in at a            temperature of 20-70° C., over a period of 4-12 h, the            metered addition being effected continuously over the entire            period or in equal portions every hour;        -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through.

It has been found that, surprisingly, a surfactant mixture having amolar ratio of anionic surfactant (A) to nonionic surfactant (B) of51:49 to 92:8 leads to interfacial tensions of <0.1 mN/m at ≥55° C. andsurfactant concentrations of <0.5% by weight. The aim is normallyvirtually quantitative anionization levels of alkyl alkoxylates, inorder to achieve a good effect. The values dictated by technicalviability are usually >92% or ≥95%. Accordingly, the competent person ofaverage skill in the art understands the aforementioned values to be therange that is sometimes typical for the anionic modification. In thecase of the alkyl ether carboxylates, this may, for example, be acarboxymethylation level of 95%. As explained in detail hereinafter, asometimes much lower carboxymethylation level is surprisingly found tohave better suitability. This is also of great significance, forexample, for the preparation of the alkyl ether carboxylates fortertiary mineral oil production, since less complex, lessenergy-intensive and hence less expensive processes can be used in orderto arrive at corresponding carboxymethylation levels. Of particularinterest in this context is a surfactant mixture having a molar ratio ofanionic surfactant (A) to nonionic surfactant (B) of 70:30 to89:11—especially if the surfactants are based on a mixture of primarylinear saturated alkyl radicals having 16 and 18 carbon atoms, and havepropyleneoxy and ethyleneoxy units in the manner described later, andespecially in the presence of a cosolvent, for example butyl diethyleneglycol. It is thus surprisingly possible to achieve interfacial tensionsof <0.01 mN/m at >55° C., even though no base or a very differentsurfactant, for example an internal olefinsulfonate, has been added.

Accordingly, it is preferable that the surfactant formulation in themethod of the invention for mineral oil production or the concentrate ofthe invention does not include any base and/or any olefinsulfonate orany alkylbenzenesulfonate (or any other organic sulfonate).

Further Details of the Invention

The present invention relates to a method for producing mineral oil fromunderground mineral oil deposits, in which an aqueous saline surfactantformulation comprising a surfactant mixture, for the purpose of loweringthe interfacial tension between oil and water to <0.1 mN/m at deposittemperature, is injected through at least one injection well into amineral oil deposit and crude oil is withdrawn through at least oneproduction well from the deposit, wherein

-   -   -   a) the mineral oil deposit has a deposit temperature of            55° C. to 150° C., a crude oil having more than 20° API and            a deposit water having more than 100 ppm of divalent            cations;        -   and        -   b) the surfactant mixture comprises at least one anionic            surfactant (A) of the general formula (I)

R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M   (I)

-   -   -   and at least one nonionic surfactant (B) of the general            formula (II)

R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H   (II),

-   -   -   wheat a molar ratio of anionic surfactant (A) to nonionic            surfactant (B) of 51:49 to 92:8 is present in the surfactant            mixture on injection and the nonionic surfactant (B) serves            as starting material for the anionic surfactant (A),        -   where        -   R¹ is a primary linear or branched, saturated or            unsaturated, aliphatic hydrocarbyl radical having 10 to 36            carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 2 to 14 carbon atoms; and        -   M is H, Na, K or NH₄; and        -   x is a number from 0 to 10; and        -   y is a number from 0 to 50; and        -   z is a number from I to 35;        -   where the sum total of x+y+z is a number from 3 to 80; and        -   where the sum total of x+y is a number >0 if R¹ is a primary            linear, saturated or unsaturated, aliphatic hydrocarbyl            radical having 10 to 36 carbon atoms;        -   and        -   c) the concentration of all the surfactants together is            0.05% to 0.49% by weight, based on the total amount of the            aqueous saline surfactant formulation.

R¹ is a primary linear or branched, saturated or unsaturated, aliphatichydrocarbyl radical having 10 to 36 carbon atoms (preferably 10 to 28,more preferably 13 to 20, especially preferably 16 to 18 carbon atoms).In a particular embodiment, saturated hydrocarbyl radicals are used. Ina particularly preferred embodiment, primary linear saturatedhydrocarbyl radicals having 16 to 18 carbon atoms are used. In anotherpreferred embodiment, primary linear unsaturated hydrocarbyl radicalshaving 18 carbon atoms are used. Accordingly, R¹ is an acyclic radical.

In the case of branched R¹ radicals, the branching level is preferablyin the range of 011-5 (preferably of 0.1-2.5, more preferably 0.5 to2.2). In this context, the term “branching level” is defined in a mannerknown in principle as the number of methyl groups in one molecule of thealcohol minus 1. The mean branching level is the statistical mean of thebranching levels of all molecules in a sample.

In a preferred embodiment, the branched R¹ radical is 2-propylheptyl,isodecyl, isoundecyl, isotridecyl, an alkyl radical having 12 to 15carbon atoms and a branching level of 0.1-0.5, an alkyl radical having13 to 15 carbon atoms and a branching level of 0.1-0.5 or an alkylradical having 16 to 17 carbon atoms and a branching level of 1.1 to1.9.

In a further preferred embodiment of the invention, R¹ is a primarybranched saturated aliphatic hydrocarbyl radical having 16 to 20 carbonatoms, being 2-hexyldodecyl, 2-octyldodecyl, or a mixture of thehydrocarbyl radicals mentioned. This is especially true when x is thenumber 0.

In a further preferred embodiment of the invention, R¹ is a primarybranched saturated aliphatic hydrocarbyl radical having 24 to 28 carbonatoms, being 2-decyltetradecyl, 2-dodecylhexadecyl, 2-decylhexadecyl or2-dodecyltetradecyl or a mixture of the hydrocarbyl radicals mentioned.This is especially true when x is the number 0.

In the above-defined general formulae, x, y and z are each naturalnumbers including 0, i.e. 0, 1, 2 etc. However, it is clear to theperson skilled in the art in the field of polyalkoxylates that thisdefinition is the definition of a single surfactant in each case. In thecase of the presence of surfactant mixtures or surfactant formulationscomprising a plurality of surfactants of the general formula, thenumbers x, y and z are each mean values over all molecules of thesurfactants, since the alkoxylation of alcohol with ethylene oxide orpropylene oxide or higher alkylene oxides (e.g. butylene oxide tohexadecene oxide) in each case affords a certain distribution of chainlengths. This distribution can be described in a manner known inprinciple by what is called the polydispersity D. D=M_(w)/M_(n) is theratio of the weight-average molar mass and the number-average molarmass. The polydispersity can be determined by methods known to thoseskilled in the art, for example by means of gel permeationchromatography.

The alkyleneoxy groups may be arranged in random distribution,alternately or in blocks, i.e. in two, three, four or more blocks.

Preferably, the x (higher alkylene)oxy, y propyleneoxy and z ethyleneoxygroups are at least partly arranged in blocks (in numerical terms,preferably to an extent of at least 50%, more preferably to an extent ofat least 60%, even more preferably to an extent of at least 70%, morepreferably to an extent of at least 80%, more preferably to an extent ofat least 90%, especially completely).

In the context of the present invention, “arranged in blocks” means thatat least one alkyleneoxy has a neighboring alkyleneoxy group which ischemically identical, such that these at least two alkyleneoxy unitsform a block.

More preferably, there then occurs, on the R¹—O radical in formula (I)or (II), a (higher alkylene)oxy block with x (higher alkylene)oxygroups, followed by a propyleneoxy block with y propyleneoxy groups andfinally an ethyleneoxy block with z ethyleneoxy groups.

Preferably, x is an integer from 0 to 10 (preferably 0 to 7, morepreferably 0 to 1 and most preferably the number 0; x may also be aninteger from 1 to 10) and/or y is an integer from 0 to 50 (preferably 0to 40, more preferably 3 to 25, especially preferably 3 to 10 or 5 to 15and even more preferably 5 to 9) and/or z is an integer from 1 to 35(preferably 1 to 30 or 3 to 30, more preferably 1 to 25, especiallypreferably 3 to 24 and even more preferably 4 to 15 and especially 5 to15), where the sum total of x+y+z is a number from 3 to 80, preferablyfrom 3 to 49 and especially preferably from 7 to 24, where the sum totalof x+y is a number >0 if R¹ is a primary linear, saturated orunsaturated, aliphatic hydrocarbyl radical having 10 to 36 carbon atoms.

In a farther particular embodiment of the invention,

-   -   -   R¹ is a primary linear or branched, saturated or            unsaturated, aliphatic hydrocarbyl radical having 10 to 36            carbon atoms; and        -   x is the number 0; and        -   y is a number from 3 to 25 (more preferably 3 to 10); and        -   z is a number from 3 to 30 (more preferably 4 to 15); and            the sum total of x+y+z is a number from 6 to 55 (more            preferably 7 to 25).

In a further particular embodiment of the invention, the sum total ofx+y+z is a number from 7 to 24.

In a further embodiment of the invention, the method has thecharacteristic feature that

-   -   -   R¹ is a primary linear or branched, saturated or            unsaturated, aliphatic hydrocarbyl radical having 10 to 36            carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 2 to 14 carbon atoms (more preferably 2); and        -   M is H, Na, K or NH₄; and        -   x is a number from 1 to 10 (more preferably 1 to 5); and        -   y is a number from 0 to 50 (more preferably 1 to 9); and        -   z is a number from 3 to 35;        -   where sum total of x+y+z is a number from 4 to 80 (more            preferably 5 to 35).

In a further embodiment of the invention, the method has thecharacteristic feature that

-   -   -   R¹ is a primary branched saturated aliphatic hydrocarbyl            radical having 10 to 36 carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 10 to 14 carbon atoms; and        -   M is H, Na, K or NH₄; and        -   x is a =Wier of 1; and        -   y is the number 0 to 20; and        -   z is a number from 3 to 35;        -   where sum total of x+y+z is a number from 4 to 45.

In a further preferred embodiment, the method has the characteristicfeature that

-   -   -   R¹ is a primary branched saturated aliphatic hydrocarbyl            radical having 10 to 36 carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 2 to 14 carbon atoms; and        -   M is H, Na, K or NH₄; and        -   x is a number from 0 to 10 (preferably 0); and        -   y is the number 0; and        -   z is a number from 3 to 35;        -   where the sum, total of x+y+z is; a number from 3 to 45.

In a further embodiment of the invention, the method has thecharacteristic feature that

-   -   -   R¹ is a primary branched saturated aliphatic hydrocarbyl            radical having 16 to 20 carbon atoms, being 2-hexyldecyl,            2-octyldecyl, 2-hexyldodecyl or 2-octyldodecyl, or a mixture            of the hydrocarbyl radicals mentioned; and        -   x is the number 0.

In a further embodiment of the invention, the method has thecharacteristic feature that

-   -   -   R¹ is a primary branched saturated aliphatic hydrocarbyl            radical having 24 to 28 carbon atoms, being            2-decyltetradecyl, 2-dodecylhexadecyl, 2-decylhexadecyl or            2-dodecyltetradecyl or a mixture of the hydrocarbyl radicals            mentioned; and        -   x is the'number 0.

In another particularly preferred embodiment of the invention, themethod has the characteristic feature that

-   -   -   R¹ is a primary linear saturated aliphatic hydrocarbyl            radical having 16 or 18 carbon atoms; and        -   R² is a linear saturated aliphatic hydrocarbyl radical            having 10 to 14 carbon atoms; and        -   M is H, Na, K or NH₄; and        -   x is the number 0; and        -   y is the number 3 to 15 (preferably 3 to 10, more preferably            5 to 9); and        -   z is a number from 3 to 35 (preferably 3 to 25, more            preferably 8 to 20);        -   where sum total of x+y+z is a number from 6 to 45.

In the above formula (I), M⁺ may also be a cation selected from thegroup of Na⁺; K⁺, Li⁺, NH₄ ⁺, H⁺,½ Mg²⁺ and ½ Ca²⁺. However, thepreferred embodiment for M⁺ is Na⁺, K⁺ or NH₄ ⁺.

It is a characteristic feature of the invention that a molar ratio ofanionic surfactant (A) of the general formula (I) to nonionic surfactant(B) of the general formula (II) of 51:49 to 92:8 is present in thesurfactant mixture or in the concentrate on injection and the nonionicsurfactant (B) serves as starting material for anionic surfactant (A).In a preferred execution of the invention, the ratio is 60:40 to 92:8,more preferably 70:30 to 92:8, especially preferably 70:30 to 89:11 andvery especially preferably 71:29 to 85:15.

In the context of the process according to the invention for tertiarymineral oil production, the use of the inventive surfactant mixturelowers the interfacial tension between oil and water to values of <0.1mN/m, preferably to <0.05 mN/m, more preferably to <0.01 mN/m. Thus, theinterfacial tension between oil and water is lowered to values in therange from 0.1 mN/m to 0.0001 mN/m, preferably to values in the rangefrom 0.05 mN/m to 0.0001 mN/m, more preferably to values in the rangefrom 0.01 mN/m to 0.0001 mN/m. The stated values relate to theprevailing deposit temperature.

A particularly preferred execution is a Wansor type III microemulsionflooding operation.

In a further preferred execution of the invention, a thickening polymerfrom the group of the biopolymers or from the group of the copolymersbased on acrylamide is added to the aqueous surfactant formulation. Thecopolymer may consist, for example, of the following units inter alia:

-   -   -   acrylamide and acrylic acid sodium salt        -   acrylamide and acrylic acid sodium salt and            N-vinylpyrrolidone        -   acrylamide and acrylic acid sodium salt and AMPS            (2-acrylamido-2-methylpropanesulfonic acid sodium salt)        -   acrylamide and acrylic acid sodium salt and AMPS            (2-acrylamido-2-methylpropanesulfonic acid sodium salt) and            N-vinylpyrrolidone.

The copolymer may also additionally comprise associative groups.Preferred copolymers are described in EP 2432807 or in WO 2014095621.Further preferred copolymers are described in U.S. Pat. No. 7,700,702.

A particularly preferred execution is a Winsor type 111microemulsion/polymer flooding operation.

In a preferred execution of the invention, it is a characteristicfeature of the process that the production of mineral oil fromunderground mineral oil deposits is a surfactant flooding method or asurfactant/polymer flooding method and not an alkali/surfactant/polymerflooding method and not a flooding method in which Na₂CO₃ is injected aswell.

In a particularly preferred execution of the invention, it is acharacteristic feature of the process that the production of mineral oilfrom underground mineral oil deposits is a Winson type III microemulsionflooding method or a Winsor type III microemulsion/polymer floodingmethod and not an alkali/Winsor type III microemulsion/polymer floodingmethod and not a flooding method in which Na₂CO₃ is injected as well.

The deposit rock may be sandstone or carbonate.

In a preferred embodiment of the invention, the deposit is a sandstonedeposit, wherein more than 70 percent by weight of sand (quartz and/orfeldspar) is present and up to 25 percent by weight of other mineralsselected from kaolinite, smectite, illite, chlorite and/or pyrite may bepresent. It is preferable that more than 75 percent by weight of sand(quartz and/or feldspar) is present and up to 20 percent by weight ofother minerals selected from kaolinite, smectite, illite, chloriteand/or pyrite may be present. It is especially preferable that more than80 percent by weight of sand (quartz and/or feldspar) is present and upto 15 percent by weight of other minerals selected from kaolinite,smectite, illite, chlorite and/or pyrite may be present.

The API gravity (American Petroleum Institute gravity) is a conventionalunit of density commonly used in the USA for crude oils. It is usedglobally for characterization and as a quality standard for crude oil.The API gravity is calculated from the relative density p_(rel) of thecrude oil at 60° F. (15.56° C.), based on water, using

API gravity−(141.5/p_(rel))−131.5,

According to the invention, the crude oil from the deposit should haveat least 20° API. Preference is given to at least 22° API. Particularprefeatme is given to at least 25° API. Very particular preference isgiven to at least 30° API.

The deposit temperature in the mineral oil deposit in which the methodof the invention is employed is, in accordance with the invention, 55 to150° C., especially 55° C. to 140° C., preferably 60° C. to 130° C.,more preferably 60° C. to 120° C. and, for example, 65° C. to 110° C.

The salts in the deposit water may especially be alkali metal salts andalkaline earth metal salts. Examples of typical cations include Na⁺, K⁺,Mg²⁺+ and/or Ca²⁺, and examples of typical anions include chloride,bromide, hydrogencarbonate, sulfate or borate. According to theinvention, the deposit water should include at least 100 ppm of divalentcations. The amount of alkaline earth metal ions may preferably be 100to 53,000 ppm, more preferably 120 ppm to 20,000 ppm and even morepreferably 150 to 6000 ppm.

In general, at least one or more than one alkali metal ion is present,especially at least Na⁺. In addition, alkaline earth metal ions can alsobe present, in which case the weight ratio of alkali metal ions/alkalineearth metal ions is generally ≥2, preferably ≥3. Anions present aregenerally at least one or mere than one halide ion(s), especially atleast CI⁻. In general, the amount of CI⁻ is at least 50% by weight,preferably at least 80% by weight, based on the sum total of all theanions.

The total amount of all the salts in the deposit water may be up to350,000 ppm (parts by weight), based on the sum total of all thecomponents in the formulation, for example 2000 ppm to 350,000 ppm,especially 5000 ppm to 250,000 ppm. If seawater is used for injection,the salt content may be 2000 ppm to 40,000 ppm, and, if formation wateris used, the salt content may be 5000 ppm to 250,000 ppm, for example10,000 ppm to 200,000 ppm.

The concert tion of all the surfactants together is 0.05% to 0.49% byweight, based on the total amount of the aqueous formulation injected.The total surfantant concentration is preferably 0.06% to 0.39% byweight, more preferably 0.08% to 0.29% by weight.

In a further preferred embodiment of the invention, at least one organiccosolvent can be added to the surfactant mixture claimed. These arepreferably completely water-miscible solvents, but it is also possibleto use solvents having only partial water miscibility. In general, thesolubility should be at least 50 g/I, preferably at least 100 g/l.Examples include aliphatic C3 to C8 alcohols, preferably C4 to C6alcohols, farther preferably C3 to C6 alcohols, which may be substitutedby 1 to 5, preferably 1 to 3, ethyleneoxy units to achieve sufficientwater solubility, Further examples include aliphatic dials having 2 to 8carbon atoms, which may optionally also have further substitution. Forexample, the cosolvent may be at least one selected from the group of2-butanol, 2-methyl-1-propanol, butyl ethylene glycol, butyl diethyleneglycol or butyl triethylene glycol.

Accordingly, it is preferable that the aqueous saline suriactantformulation comprises, as well as the anionic surfactant (A) of thegeneral formula (I) and the nonionic surfactant (B) of the generalformula (II), also a cosolvent selected from the group of the aliphaticalcohols having 3 to 8 carbon atoms or from the group of the alkylmonoethylene glycols, the alkyl diethylene glycols or the alkyltriethylene glycols, where the alkyl radical is an aliphatic hydrocarbylradical having 3 to 6 carbon atoms.

Particular preference is given to a method wherein the mixture ofanionic surfactant (A) of the general formula (I) and nonionicsurfactant (B) of the general formula (II) is provided in the form of aconcentrate comprising 20% by weight to 70% by weight of the surfactantmixture, 10% by weight to 40% by weight of water and 10% by weight to40% by weight of a cosolvent, based on the total amount of theconcentrate, where the cosolvent is selected from the group of thealiphatic alcohols having 3 to 8 carbon atoms or from the group of thealkyl monoethylene glycols, the alkyl diethylene glycols or the alkyltriethylene glycols, where the alkyl radical is an aliphatic hydrocarbylradical having 3 to 6 carbon atoms, and the concentrate is free-flowingat 20° C. and has a viscosity at 40° C. of <1500 mPas at 200 Hz.

It is additionally preferable that the concentrate comprises 0.5% to 20%by weight (preferably 1% to 15%, more preferably 2% to 10%, by weight)of a mixture comprising NaCl and diglycolic acid disodium salt, whereNaCl is present in excess relative to diglycolic acid disodium salt.

It is most preferable that the concentrate comprises butyl diethyleneglycol as cosolvent.

A further execution of the invention is a method wherein aqueous salinesurfactant formulation comprises, as well as the anionic surfactant (A)of the general formula (I) and the nonionic surfactant (B) of thegeneral formula (II), also further surfactants (C) which are notidentical to the surfactants (A) or (B), and

-   -   -   are from the group of the alkylbenzenesulfonates,            alpha-olefinsulfonates, internal olefinsulfonates,            paraffinsulfonates, where the surfactants have 14 to 28            carbon atoms;            -   and/or        -   are selected from the group of the alkyl ethoxylates and            alkyl polyglucosides, where the particular alkyl radical has            8 to 18 carbon atoms.

For the surfactants (C), particular preference is given to alkylpolyglucosides which have been formed from primary linear fatty alcoholshaving 8 to 14 carbon atoms and have a glucosidation level of 1 to 2,and alkyl ethoxylates which have been formed from primary alcoholshaving 10 to 18 carbon atoms and have an ethoxylation level of 3 to 25.

The nonionic surfactants (B) of the general formula (II) can be formedas follows. First of all, it requires the preparation of a correspondingalcohol which can be prepared as follows by way of example:

-   -   -   primary linear aliphatic alcohols are prepared by            hydrogenating fatty acids (prepared from natural vegetable            or animal fats and oils) or by hydrogenating fatty acid            methyl esters. Alternatively, they can be prepared by the            Ziegler process by oligomerizing ethylene over an aluminum            catalyst and then releasing the alcohol by adding water.        -   primary branched aliphatic alcohols can be prepared by            hydroformylation (reaction with carbon monoxide and            hydrogen) of alkenes (oxo process alcohols). The alkenes may            be oligomers of ethylene, propylene and/or butylene. The            oligomerization may give rise to alpha-olefins, and also            olefins having an internal double bond. Through olefin            metathesis of the alkenes, further variations are possible.            A further access route to alkenes is the dehydrogenation of            alkanes and paraffins.        -   primary branched aliphatic alcohols can be prepared by            Guerbet reaction (dimerization of alcohols with elimination            of water in the presence of base and at elevated            temperature) of primary alcohols (Guerbet alcohols). Further            details can be found, for example, in WO2013060670.

Subsequently, the primary alcohols R¹OH are alkoxylated to give thecorresponding nonionic surfactants (B) of the general formula (II). Theperformance of such alkoxylations is known in principle to those skilledin the art. It is likewise known to those skilled in the art that thereaction conditions, especially the selection of the catalyst, caninfluence the molecular weight distribution of the alkoxylates.

The surfactants according to the general formula can preferably beprepared by base-catalyzed alkoxylation. In this case, the alcohol R¹OHcan be admixed in a pressure reactor with alkali metal hydroxides (e.g.NaOH, KOH, CsOH), preferably potassium hydroxide, or with alkali metalalkoxides, for example sodium methoxide or potassium methoxide. Water(or MeOH) still present in the mixture can be drawn off by means ofreduced pressure (for example <100 mbar) and/or increasing thetemperature (30 to 150° C.) Thereafter, the alcohol is present in theform of the corresponding alkoxide. This is followed by inertizationwith inert gas (for example nitrogen) and stepwise addition of thealkylene oxide(s) at temperatures of 60 to 180° C. up to a pressure ofnot more than 20 bar (preferably not more than 10 bar). In a preferredembodiment, the alkylene oxide is metered in initially at 120° C. In thecourse of the reaction, the heat of reaction released causes thetemperature to rise up to 170° C. In a further preferred embodiment ofthe invention, the higher alkylene oxide (e.g, butylene oxide orhexadecene oxide) is first added at a temperature in the range from 100to 145° C., then the propylene oxide is added at a temperature in therange from 100 to 145° C., and subsequently the ethylene oxide is addedat a temperature in the range from 120 to 165° C. At the end of thereaction, the catalyst can, for example, be neutralized by adding acid(for example acetic acid or phosphoric acid) and be filtered off ifrequired. However, the material may also remain unneutralized.

The alkoxylation of the alcohols R¹OH can also be undertaken by means ofother methods, for example by acid-catalyzed alkoxylation. In addition,it is possible to use, for example, double hydroxide clays, as describedin DE 4325237 A1, or it is possible to use double metal cyanidecatalysts (DMC catalysts). Suitable DMC catalysts are disclosed, forexample, in DE 10243361 A1, especially in paragraphs [0029] to [0041]and the literature cited therein. For example, it is possible to usecatalysts of the Zn—Co type. To perform the reaction, the alcohol R¹OHcan be admixed with the catalyst, and the mixture dewatered as describedabove and reacted with the alkylene oxides as described. Typically notmore than 1000 ppm of catalyst based on the mixture are used, and thecatalyst can remain in the product owing to this small amount. Theamount of catalyst may generally be less than 1000 ppm, for example 250ppm or less.

The anionic surfactants (A) of the general formula (I) can be preparedfrom the nonionic surfactants (B) of the general formula (II).

In this case, the invention preferably relates to a method wherein theanionic surfactant (A) of the general formula (I) is prepared byreacting the nonionic surfactant (B) of the general formula (II), whilestirring, with chloroacetic acid or chloroacetic acid sodium salt in thepresence of alkali metal hydroxide or aqueous alkali metal hydroxide,with removal of water of reaction such that the water content in thereactor is kept at a value of 0.2% to 1.7% (preferably 0.3% to 1.5%)during the carboxymethylation by applying reduced pressure and/or bypassing nitrogen through. Particular preference is given to the methodfor surfactants comprising propyleneoxy units. It is even morepreferable when the surfactants are additionally those based on linearC16C18 fatty alcohol.

A further preferred embodiment of the invention relates to a methodwherein

-   -   -   aqueous NaOH (preferably 40-80% strength, more preferably            45-55% strength) as alkali metal hydroxide and aqueous            chloroacetic acid (preferably 75-85% strength) are used in            the carboxymethylation, using NaOH in relation to the            chloroacetic acid in a ratio of 2 eq (molar equivalent): 1            eq to 2.2 eq:1 eq;

    -   and        -   the nonionic surfactant (B) has been prepared either via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH or via an            alkoxylation using a double metal cyanide catalyst, and the            alkoxylation catalyst has not been neutralized and not been            removed after the alkoxylation has ended;

    -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged together in the reactor in the            carboxymethylation and the sodium hydroxide and chloroacetic            acid are metered in in parallel at a temperature of            60-110° C. (preferably 70-100° C.) over a period of 1-7 h            (preferably 1-6 h), the metered addition over the entire            period being effected continuously or in equal portions            every hour, and the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to the            chloroacetic acid being 1 eq:1 eq to 1 eq:1.9 eq (preferably            1 eq:1 eq to 1 eq:1.5 eq, more preferably 1 eq:1 eq to 1 eq            1.35 eq);

    -   and

    -   the water content in the reactor is kept predominantly at an        average value of 0.2% to 1.7% during the carboxymethylation by        applying reduced pressure and/or by passing nitrogen through.

A further preferred embodiment of the invention rebates to a methodwherein

-   -   -   NaOH as alkali metal hydroxide and chloroacetic acid sodium            salt are used in the carboxymethylation, using NaOH in            relation to the chloroacetic acid sodium salt in a ratio of            1 eq (molar equivalent): 1 eq to 1 eq:1.9 eq;

    -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation (preferably <5 mol % of base as            alkoxylation catalyst) using KOH or NaOH or CsOH and is            preferably used in unneutralized form in the            carboxymethylation;

    -   and        -   the nonionic surfactant (B) of the general formula (II) is            initially charged in the reactor in the carboxymethylation            together with NaOH or aqueous NaOH (preferably 40-80%            strength), where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to NaOH is 1 eq:1            eq to 1 eq:1.5 eq (preferably 1 eq:1 eq to 1 eq:1.35 eq), a            temperature of 60-110° C. is set, and the nonionic            surfactant (B) of the general formula (II) is converted to            the corresponding sodium salt            R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na by            applying reduced pressure and/or passing nitrogen through            and, at a temperature of 60-110° C., the chloroacetic acid            sodium salt is metered in completely or preferably over a            period of 4-12 h, where the stoichiometric ratio of nonionic            surfactant (B) of the general formula (II) to the            chloroacetic acid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq            (preferably 1 eq:1 eq to 1 eq:1.5 eq) and where the metered            addition over the entire period is effected continuously or            in equal portions every hour;

    -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% during the carboxymethylation by applying reduced            pressure and/or by passing nitrogen through.

A further preferred embodiment of the invention relates to a methodwherein

-   -   -   solid NaOH as alkali metal hydroxide and chloroacetic acid            sodium salt are used in the carboxymethylation, using NaOH            in relation to the chloroacetic acid sodium salt in a ratio            of 1 eq (molar equivalent):1 eq to 1.1 eq:1 eq;

    -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation using KOH or NaOH or CsOH and            then neutralized with acetic acid and is used in the            carboxymethylation together with initially 0.5-1.5% water;

    -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq;1.5 eq, especially preferably 1 eq:1 eq to 1 eq:1.35 eq),            and the sodium hydroxide is metered in at a temperature of            20-70° C. over a period of 4-12 h, the metered addition            being effected continuously over the entire period or in            equal portions every hour;

    -   and

    -   the water content in the reactor is kept at a value of 0.2% to        1.7% (preferably 0.3% to 1.5%) during the carboxymethylation by        applying reduced pressure and/or by passing nitrogen through.

Another preferred embodiment of the invention relates to a methodwherein

-   -   -   solid NaOH as alkali metal hydroxide and chloroacetic acid            sodium salt are used in the carboxymethylation, using NaOH            or, in the case of a basic alkoxylate, the sum total of NaOH            and R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)₂—K or            the sum total in the case of a basic alkoxylate of NaOH and            R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na or,            in the case of a basic alkoxylate, the sum total of NaOH and            R¹—O—(CH₂C(R²)HO)_(z)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Cs in            relation to the chloroacetic acid sodium salt in a ratio of            1.1 eq (molar equivalent):1 eq to 1 eq:1.5 eq (preferably 1            eq:1 eq to 1.1 eq:1 eq), where the ratio of nonionic            surfactant (B) of the general formula (II):NaOH is 1 eq:1 eq            to 1 eq:1.5 eq;

    -   and        -   the nonionic surfactant (B) has been prepared via a            base-catalyzed alkoxylation using KOH or NaOH or CsOH or a            mixture of NaOH and KOH, and is used in the            carboxymethylation either in neutralized and filtered (i.e.            salt-free) form or in the form of an unneutralized basic            alkoxylate (preferably <5 mol % of base as alkoxylation            catalyst);

    -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq: 1.5 eq, especially preferably 1 eq:1 eq to 1 eq:1.35            eq), and the sodium hydroxide is metered in at a temperature            of 20-70° C. (preferably 40 to 60° C.) over a period of 4-12            h, the metered addition being effected continuously over the            entire period or in equal portions every hour;

    -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% (preferably 0.3% to 1.5%) during the            carboxymethylation by applying reduced pressure and/or by            passing nitrogen through.

Another preferred embodiment of the invention relates to a methodwherein

-   -   -   solid NaOH as alkali metal hydroxide and chloroacetic acid            sodium salt are used in the carboxymethylation, using NaOH            in relation to the chloroacetic acid sodium salt in a ratio            of 1 eq (molar equivalent):1 eq to 1.1 eq:1 eq;

    -   and        -   the nonionic surfactant (B) has been prepared via an            alkoxylation using double metal cyanide catalysis;

    -   and        -   chloroacetic acid sodium salt and the nonionic            surfactant (B) of the general formula (II) are initially            charged together in the reactor in the carboxymethylation,            where the stoichiometric ratio of nonionic surfactant (B) of            the general formula (II) to the chloroacetic acid sodium            salt is 1 eq:1 eq to 1 eq:1.9 eq (preferably 1 eq:1 eq to 1            eq:1.5 eq, especially preferably 1 eq:1 eq to 1 eq:1.35 eq),            and the sodium hydroxide is metered in at a temperature of            20-70° C. over a period of 4-12 h, the metered addition            being effected continuously over the entire period or in            equal portions every hour;

    -   and        -   the water content in the reactor is kept at a value of 0.2%            to 1.7% (preferably 0.3% to 1.5%) during the            carboxymethylation by applying reduced pressure, and/or by            passing nitrogen through.

A preferred embodiment of the invention is a production method accordingto the above-specified executions for production, in order to prepare asurfactant mixture of anionic surfactant (A) of the general formula (I)and nonionic surfactant (B) of the general formula (II), wherein a molarratio of anionic surfactant (A) to nonionic surfactant (B) of 51:49 to92:8 (preferably 70:30 to 89:11) is present in the surfactant mixture atthe end of the reaction.

Additionally preferably, the methods of the invention for mineral oilproduction comprise the method steps of the production methods of theinvention that are upstream of the injection step.

A particularly preferred embodiment of the invention is a productionmethod according to the above-specified executions for production, inorder to prepare a surfactant mixture of anionic surfactant (A) of thegeneral formula (I) and nonionic surfactant (B) of the general formula(II), wherein a molar ratio of anionic surfactant (A) to nonionicsurfactant (B) of 51:49 to 92:8 (preferably 70:30 to 89:11) is presentin the surfactant mixture at the end of the reaction, and thesurfactants comprise propyleneoxy units. It is even more preferable whenthe surfactants are additionally those based on linear C16C18 fattyalcohol.

Likewise in accordance with the invention is a concentrate as alreadyspecified above, composed of anionic surfactant (A) of the generalformula (I) and nonionic surfactant (B) of the general formula (II),wherein a molar ratio of anionic surfactant (A) to nonionic surfactant(B) of 51:49 to 92:8 (preferably 70:30 to 89:11) is present in theconcentrate.

Method of Mineral Oil Production

The above-described method of mineral oil production with the aid of theclaimed surfactant mixture of anionic surfactant (A) of the generalformula (I) and the nonionic surfactant (B) of the general formula (II)can optionally be conducted with the addition of further methods. Forinstance, it is optionally possible to add a polymer or a foam formobility control. The polymer can optionally be injected into thedeposit together with the surfactant formulation, followed by thesurfactant formulation. It can also be injected only with the surfactantformulation or only after surfactant formulation. The polymers may becopolymers based on acrylamide or a biopolymer. The copolymer mayconsist, for example, of the following units inter alia:

-   -   acrylamide and acrylic acid sodium salt    -   acrylamide and acrylic acid sodium salt and N-vinylpyrrolidone    -   acrylamide and acrylic acid sodium salt and AMPS        (2-acrylamido-2-methylpropanesulfonic acid sodium salt)    -   acrylamide and acrylic acid sodium salt and AMPS        (2-acrylamido-2-methylpropanesulfonic acid sodium salt) and        N-vinylpyrrolidone.

The copolymer may also additionally comprise associative groups. Usablecopolymers are described in EP 2432807 or in WO 2014095621. Furtherusable copolymers are described in US 7700702.

The polymers can be stabilized by addition of further additives such asbiocides, stabilizers, free radical scavengers and inhibitors.

The foam can be produced at the deposit surface or in situ in thedeposit by injection of gases such as nitrogen or gaseous hydrocarbonssuch as methane, ethane or propane. The foam can be produced andstabilized by adding the surfactant mixture claimed or else furthersurfactants.

Optionally, it is also possible to add a base such as alkali metalhydroxide or alkali metal carbonate to the surfactant formulation, inwhich case it is combined with complexing agents or polyacrylates inorder to prevent precipitation as a result of the presence of polyvalentcations. In addition, it is also possible to add a cosolvent to theformulation.

This gives rise to the following (combined) methods:

-   -   surfactant flooding    -   Winsor type III microemulsion flooding    -   surfactant/polymer flooding    -   Winsor type III microemulsion/polymer flooding    -   alkali/surfactant/polymer flooding    -   alkali/Winsor type III microemulsion/polymer flooding    -   surfactant/foam flooding    -   Winsor type III microemulsion/foam flooding    -   alkali/surfactant/foam flooding    -   alkali/Winsor type Ill microemulsion/foam flooding

In a preferred embodiment of the invention, one of the first fourmethods is employed (surfactant flooding, Winsor type III microemulsionflooding, surfactant/polymer flooding or Winsor type IIImicroemulsion/polymer flooding). Particular preference is given toWinsor type III microemulsion/polymer flooding.

In Winsor type III microemulsion/polymer flooding, in the first step, asurfactant formulation is injected with or without polymer. Thesurfactant formulation, on contact with crude oil, results in theformation of a Winsor type III microemulsion. In the second step, onlypolymer is injected. In the first step in each case, it is possible touse aqueous formulations having higher salinity than in the second step.Alternatively, both steps can also be conducted with water of equalsalinity.

In one embodiment, the methods can of course also be combined with waterflooding. In the case of water flooding, water is injected into amineral oil, deposit through at least one injection well, and crude oilis withdrawn from the deposit through at least one production well. Thewater may be freshwater or saline water such as seawater or depositwater. After the water flooding, the method of the invention may beemployed.

To execute the method of the invention, at least one production well andat least one injection well are sunk into the mineral oil deposit. Ingeneral, a deposit is provided with several injection wells and withseveral production wells. An aqueous formulation of the water-solublecomponents described is injected through the at least one injection wellinto the mineral oil deposit, and crude oil is withdrawn from thedeposit through at least one production well. As a result of thepressure generated by the aqueous formulation injected, called the“flood”, the mineral oil flows in the direction of the production welland is produced via the production well. The term “mineral oil” in thiscontext of course does not just mean single-phase oil; instead, the termalso encompasses the usual crude oil-water emulsions. It will be clearto the person skilled in the art that a mineral oil deposit may alsohave a certain temperature distribution. Said deposit temperature isbased on the region of the deposit between the injection and productionwells which is covered by the flooding with aqueous solutions. Methodsof determining the temperature distribution of a mineral oil deposit areknown in principle to those skilled in the art. The temperaturedistribution is generally determined from temperature measurements atparticular sites in the formation in combination with simulationcalculations; the simulation calculations also take account of theamounts of heat introduced into the formation and the amounts of heatremoved from the formation.

The method of the invention can especially be employed in mineral oildeposits having an average porosity of 5 mD to 4 D, preferably 50 mD to2 D and more preferably 200 mD to 1 D. The permeability of a mineral oilformation is reported by the person skilled in the art in the unit“darcy” (abbreviated to “D” or “mD” for “millidarcies”), and can bedetermined from the flow rate of a liquid phase in the mineral oilformation as a function of the pressure differential applied. The flowrate can be determined in core flooding tests with drill cores takenfrom the formation. Details of this can be found, for example, in K.Weggen, G. Pusch, II. Rischmüller in “Oil and Gas”, pages 37 ff,Ullmann's Encyclopedia of Industrial Chemistry, Online Edition,Wiley-VCH, Weinheim 2010. It will be clear to the person skilled in theart that the permeability in a mineral oil deposit need not behomogeneous, but generally has a certain distribution, and thepermeability reported for a mineral oil deposit is accordingly anaverage permeability.

To execute the method, an aqueous formulation is used, comprising, aswell as water, at least the described surfactant mixture of anionicsurfactant (A) of the general formula (I) and the nonionic surfactant(B) of the general formula (II).

The formulation is made up in water comprising salts. Of course, theremay also be mixtures of different salts. For example, it is possible touse seawater to make up the aqueous formulation, or it is possible touse produced formation water, which is reused in this way. In the caseof offshore production platforms, the formulation is generally made upin seawater. In the case of onshore production facilities, the polymercan advantageously first be dissolved in fresh water and the solutionobtained can be diluted to the desired use concentration with formationwater. The deposit water or seawater should include at least 100 ppm ofdivalent cations.

The salts may especially be alkali metal salts and alkaline earth metalsalts. Examples of typical anions include Na⁺, K⁺, Mg²⁺ and/or Ca²⁺, andexamples of typical cations include chloride, bromide,hydrogencarbonate, sulfate or borate.

In general, at least one or more than one alkali metal ion is present,especially at least Na⁺. In addition, alkaline earth metal ions are alsobe present, in which case the weight ratio of alkali metal ions/alkalineearth metal ions is generally ≥2, preferably ≥3. Anions present aregenerally at least one or more than one halide ion(s), especially atleast Cl⁻. In general, the amount of Cl⁻ is at least 50% by weight,preferably at least 80% by weight, based on the sum total of all theanions.

The total amount of all the salts in the aqueous formulation may be upto 350,000 ppm (parts by weight), based on the sum total of all thecomponents in the formulation, for example 2000 ppm to 350,000 ppm,especially 5000 ppm to 250,000 ppm. If seawater is used to make up theformulation, the salt content may be 2000 ppm to 40,000 ppm, and, ifformation water is used, the salt content may be 5000 ppm to 250,000ppm, for example 10,000 ppm to 200,000 ppm. The amount of alkaline earthmetal ions may preferably be 100 to 53,000 ppm, more preferably 120 ppmto 20,000 ppm and even more preferably 150 to 6000 ppm.

Additives can be used, for example, in order to prevent unwanted sideeffects, for example the unwanted precipitation of salts, or in order tostabilize the polymer used. The polymer-containing formulations injectedinto the formation in the flooding process flow only very gradually inthe direction of the production well, meaning that they remain underformation conditions in the formation for a prolonged period.Degradation of the polymer results in a decrease in the viscosity. Thiseither has to be taken into account through the use of a higher amountof polymer, or else it has to be accepted that the efficiency of themethod will worsen. In each case, the economic viability of the methodworsens. A multitude of mechanisms may be responsible for thedegradation of the polymer. By means of suitable additives, the polymerdegradation can be prevented or at least delayed according to theconditions.

In one embodiment of the invention, the aqueous formulation usedcomprises at least one oxygen scavenger. Oxygen scavengers react withoxygen which may possibly be present in the aqueous formulation and thusprevent the oxygen from being able to attack the polymer or polyethergroups. Examples of oxygen scavengers comprise sulfites, for exampleNa₂SO₃, bisulfites, phosphites, hypophosphites or dithionites.

In a further embodiment of the invention, the aqueous formulation usedcomprises at least one free radical scavenger. Free radical scavengerscan be used to counteract the degradation of the polymer by freeradicals. Compounds of this kind can form stable compounds with freeradicals. Free radical scavengers are known in principle to thoseskilled in the art. For example, they may be stabilizers selected fromthe group of sulfur compounds, secondary amines, sterically hinderedamines, N-oxides, nitroso compounds, aromatic hydroxyl compounds orketones. Examples of sulfur compounds include thiourea, substitutedthioureas such as N,N′-dimethylthiourea, N,N′-diethylthiourea,N,N′-diphenylthiourea, thiocyanates, for example ammonium thiocyanate orpotassium thiocyanate, tetramethylthiuram disulfide, and mercaptans suchas 2-mercaptobenzothiazole or 2-mercaptobenzimidazole or salts thereof,for example the sodium salts, sodium dimethyldithiocarbamate,2,2′-dithiobis(benzothiazole), 4,4′-thiobis(6-t-butyl-m-cresol). Furtherexamples include phenoxazine, salts of carboxylated phenoxazine,carboxylated phenoxazine, methylene blue, dicyandiamide, guanidine,cyanamide, paramethoxyphenol, sodium salt of paramethoxyphenol,2-methylhydroquinone, salts of 2-methylhydroquinone,2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole, 8-hydroxyquinoline,2,5-di(t-amyl)-hydroquinone, 5-hydroxy-1,4-naphthoquinone,2,5-di(t-amyl)hydroquinone, dimedone, propyl 3,4,5-trihydroxybenzoate,ammonium N-nitrosophenyIhydroxylamine,4-hydroxy-2,2,6,6tetramethyloxypiperidine,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and1,2,2,6,6-pentamethyl-4-piperidinol. Preference is given to stericallyhindered amines such as 1,2,2,6,6-pentamethyl-4-piperidinol and sulfurcompounds, mercapto compounds, especially 2-mercaptobenzothiazole or2-mercaptobenzimidazole or salts thereof, for example the sodium salts,and particular preference is given to 2-mercaptobenzothiazole or saltsthereof.

In a further embodiment of the invention, the aqueous formulation usedcomprises at least one sacrificial reagent. Sacrificial reagents canreact with free radicals and thus render them harmless. Examples includeespecially alcohols. Alcohols can be oxidized by free radicals, forexample to ketones. Examples include monoalcohols and polyalcohols, forexample 1-propanol, 2-propanol, propylene glycol, glycerol, butanediolor pentaerythritol.

In a further embodiment of the invention, the aqueous formulation usedcomprises at least one complexing agent. It is of course possible to usemixtures of various complexing agents, Complexing agents are generallyanionic compounds which can complex especially divalent andhigher-valency metal ions, for example Mg²⁺ or Ca²⁺. In this way, it ispossible, for example, to prevent any unwanted precipitation. Inaddition, it is possible to prevent any polyvalent metal ions presentfrom crosslinking the polymer by means of acidic groups present,especially COOH group. The complexing agents may especially becarboxylic acid or phosphonic acid derivatives. Examples of complexingagents include ethylenediaminetetraacetic acid (EDTA),ethylenediaminesuccinic acid (EDDS),diethylenetriaminepentamethylenephosphonic acid (DTPMP),methylglycinediacetic acid (MGDA) and nitrilotriacetic acid (NTA). Ofcourse, the corresponding salts of each may also be involved, forexample the corresponding sodium salts. In a particularly preferredembodiment of the invention, MGDA is used as complexing agent

As an alternative to or in addition to the abovementioned chelatingagents, it is also possible to use polyacrylates.

In a further embodiment of the invention, the formulation comprises atleast one organic cosolvent. These are preferably completelywater-miscible solvents, but it is also possible to use solvents havingonly partial water miscibility. In general, the solubility should be atleast 50 g/l, preferably at least 100 g/l. Examples include aliphatic C₄to C₈ alcohols, preferably C₄ to C₆ alcohols, which may be substitutedby 1 to 5, preferably 1 to 3, ethyleneoxy units to achieve sufficientwater solubility. Further examples include aliphatic dials havMg 2 to 8carbon atoms, which may optionally also have further substitution. Forexample, the cosolvent may be at least one selected from the group of2-butanol, 2 methyl-1-propanol, butylglycol, butyldiglycol andbutyltriglycol.

The concentration of the polymer in the aqueous formulation is fixedsuch that the aqueous formulation has the desired viscosity for the enduse. The viscosity of the formulation should generally be at least 5mPas (measured at 25° C. and a shear rate of 7 s⁻¹), preferably at least10 mPas.

According to the invention, the concentration of the polymer in theformulation is 0.02% to 0% by weight, based on the sum total of all thecomponents of the aqueous formulation. The amount is preferably 0.05% to0.5% by weight, more preferably 0.1% to 0.3% by weight and, for example,0.1% to 0.2% by weight.

The aqueous polymer-comprising formulation can be prepared by initiallycharging the water, sprinkling the polymer in as a powder and mixing itwith the water. Apparatus for dissolving polymers and injecting theaqueous solutions into underground formations is known in principle tothose skilled in the art.

The injecting of the aqueous formulation can be undertaken by means ofcustomary apparatuses. The formulation can be injected into one or moreinjection wells by means of customary pumps. The injection wells aretypically lined with steel tubes cemented in place, and the steel tubesare perforated at the desired point. The formulation enters the mineraloil formation from the injection well through the perforation. Thepressure applied by means of the pumps, in a manner known in principle,is used to fix the flow rate of the formulation and hence also the shearstress with which the aqueous formulation enters the formation. Theshear stress on entry into the formation can be calculated by the personskilled in the art in a manner known in principle on the basis of theHagen-Poiseuille law, using the area through which the flow passes onentry into the formation, the mean pore radius and the volume flow rate.The average permeability of the formation can be found as described in amanner known in principle. Naturally, the greater the volume flow rateof aqueous polymer formulation injected into the formation, the greaterthe shear stress.

The rate of injection can be fixed by the person skilled in the artaccording to the conditions in the formation. Preferably, the shear rateon entry of the aqueous polymer formulation into the formation is atleast 30,000 s⁻¹, preferably at least 60,000 s⁻¹ and more preferably atleast 90,000 s⁻¹.

In one embodiment of the invention, the method of the invention is aflooding method in which a base and typically a complexing agent or apolyacrylate is used. This is typically the case when the proportion ofpolyvalent cations in the deposit water is low (100-400 ppm). Anexception is sodium metaborate, which can be used as a base in thepresence of significant amounts of polyvalent cations even withoutcomplexing agent.

The pH of the aqueous formulation is generally at least 8, preferably atleast 9, especially 9 to 13, preferably 10 to 12 and, for example, 10.5to 11.

In principle, it is possible to use any kind of base with which thedesired pH can be attained, and the person skilled in the art will makea suitable selection. Examples of suitable bases include alkali metalhydroxides, for example NaOH or KOH, or alkali metal carbonates, forexample Na₂CO₃. In addition, the bases may be basic salts, for examplealkali metal salts of carboxylic acids, phosphoric acid, or especiallycomplexing agents comprising acidic groups in the base form, such asEDTANa₄.

Mineral oil typically also comprises various carboxylic acids, forexample naphthenic acids, which are converted to the corresponding saltsby the basic formulation. The salts act as naturally occurringsurfaetants and thus support the process of oil removal.

With complexing agents, it is advantageously possible to preventunwanted precipitation of sparingly soluble salts, especially Ca and Mgsalts, when the alkaline aqueous formulation comes into contact with thecorresponding metal ions and/or aqueous formulations for the processcomprising corresponding salts are used. The amount of complexing agentsis selected by the person skilled in the art. It may, for example, be0.1% to 4% by weight, based on the sum total of all the components ofthe aqueous formulation.

In a particularly preferred embodiment of the invention, however, amethod of mineral oil production is employed in which no base (e.g.alkali metal hydroxides or alkali metal carbonates) is used.

The following examples are intended to illustrate the invention and itsadvantages in detail:

Preparation of the Alkyl Ether Alcohols (B):

Abbreviations Used:

-   EO ethyteneoxy-   PO propyleneoxy-   BuO 1,2-butyleneoxy

For the synthesis, the following alcohols were used:

Alcohol Description C₁₆C₁₈ Commercially available tallow fatty alcoholmixture consisting of linear saturated primary C₁₆H₃₃—OH and C₁₈H₃₇—OHC₁₆C₁₈C₂₀ Mixture of alcohols obtained from a Guerbet reaction Guerbetof n-octanol and n-decanol: 2-hexyldecan-1-ol, 2- octyldecan-1-ol,2-hexyldodecan-1-ol or 2-octyldodecan- 1-ol 2PH Commerically availableGuerbet alcohol 2-propylheptan- 1-ol C₁₀H₂₁—OH

Alkyl Ether Alcohol 1: C16C18-3 PO-10 EO—H by KOH Catalysis, Desalinated

Corresponds to surfactant of the general formula (II)R1-O—(CH2C(R2)HO)_(x)—(CH2C(CH3)HO)y-(CH2CH2O)z-H with R1=C16H33/C18H37,x=0, y=3 and z=10

A 2 L pressure autoclave with anchor stirrer was initially charged with384 g (1.5 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 51 g of 50% aqueous KOH solution (0.046 mol of KOH, 2.6 g ofKOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N2.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,262 g (4,5 mol) of propylene oxide were metered in at 130° C. within 2h; pmax was 4.0 bar absolute. The mixture was stirred at 130° C. for afurther 2 h. 661 g (15 mol) of ethylene oxide were metered in at 130° C.within 5 h; pmax was 6.0 bar absolute. The mixture was left to react for1 h until Ow pressure was constant, cooled down to 100° C. anddecompressed to 1.0 bar absolute. A vacuum of <10 mbar was applied andresidual oxide was drawn off for 2 h. The vacuum was broken with N2 andthe product was decanted at 80° C. under N2. 3 percent by weight ofAmbosol (silicate for neutralization) were added, and the mixture wasstirred at 100° C. and <10 mbar for 3 h. The vacuum was broken with N2and the reaction mixture was pressure-filtered through a Seitz K900filter. Analysis (mass spectrum, GPC, 1H NMR in CDCl3, 1H NMR in MeOD)confirmed the mean composition C16C18-3 PO-10 ED-H.

Alkyl ether alcohol 2: C16C18-3 PO-10 EO—H by KOH catalysis, neutralizedwith acetic acid

A 2 L pressure autoclave with anchor stirrer was initially charged with384 g (1.5 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 5.2 g of 50% aqueous KOH solution (0.046 mol of KOH, 2.6 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,262 g (4.5 mol) of propylene oxide were metered in at 130° C. within 2h; P_(max) was 4.0 bar absolute. The mixture was stirred at 130° C. fora further 2 h. 661 g (15 mol) of ethylene oxide were metered in at 130°C. within 5 h; P_(max) was 6.0 bar absolute. The mixture was left toreact for 1 h until the pressure was constant, cooled down to 100° C.and decompressed to 1.0 bar absolute. A vacuum of <10 mbar was appliedand residual oxide was drawn off for 2 h. The vacuum was broken with N₂,the product was cooled to 80° C. and 2.8 g of acetic acid (0.046 mol)were added. The product was then decanted at 80° C. under N₂. Analysis(mass spectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD) confirmed the meancomposition C16C18-3 PO-10 EO—H.

Alkyl Ether Alcohol 3: C16C18-3 PO-10 BO—H by KOH Catalysis, Basic

A 2 L pressure autoclave with anchor stirrer was initially charged with384 g (1.5 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 5.2 g of 50% aqueous KOH solution (0.046 mol of KOH, 2.6 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,262 g (4.5 mol) of propylene oxide were metered in at 130° C. Within 2h; P_(max) was 4.0 bar absolute. The mixture was stirred at 130° C. fora further 2 h. 661 g (15 mol) of ethylene oxide were metered in at 130°C. within 5 h; P_(max) was 6.0 bar absolute. The mixture was left toreact for 1 h until the pressure was constant, cooled down to 100° C.and decompressed to 1.0 bar absolute. A vacuum of <10 mbar was appliedand residual oxide was drawn off for 2 h. The vacuum was broken with N₂and the product was decanted at 80° C. under N₂. Analysis (massspectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD) confirmed the meancomposition C16C18-3 PO-10 EO—H.

Alkyl Ether Alcohol 4: C16C18-3 PO-10 EO—H by NaOH Catalysis, Basic

A 2 L pressure autoclave with anchor stirrer was initially charged with384 g (1.5 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 5.2 g of 50% aqueous NaOH solution (0.065 mol of NaOH, 2.6 gof NaOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,262 g (4.5 mol) of propylene oxide were metered in at 130° C. within 2h; P_(max) was 5.0 bar absolute. The mixture was stirred at 130° C. fora further 2 h. 661 g (15 mol) of ethylene oxide were metered in at 130°C. within 5 h; was 6.0 bar absolute. The mixture was left to react for 1h until the pressure was constant, cooled down to 100° C. anddecompressed to 1.0 bar absolute. A vacuum of <10 mbar was applied andresidual oxide was drawn off for 2 h. The vacuum was broken with N₂ andthe product was decanted at 80° C. under N₂. Analysis (mass spectinm,GPC, 1H NMR in CDCl₃, 1H NMR in MeOD) confirmed the mean compositionC16C18-3 PO-10 EO—H.

Alkyl Ether Alcohol 5: C16C18-7 PO-10 EO—H by KOH Catalysis, Desalinated

Corresponds to surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)-13 H withR¹=C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10.

A 2 L pressure autoclave with anchor stirrer was initially charged with256 g (1.0 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 2.2 g of 50% aqueous KOH solution (0.020 mol of KOH, 1.1 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 140° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revelations per minute,407 g (7 mol) of propylene oxide were metered in at 140° C. within 5 h;P_(max) was 6.0 bar absolute. The mixture was stirred at 140° C. for afurther 2 h. 441 g (10 mol) of ethylene oxide were metered in at 140° C.within 10 h; P_(max) was 5.0 bar absolute. The mixture was left to reactfor 1 h until the pressure was constant, cooled down to 100° C. anddecompressed to 1.0 bar absolute, A vacuum of <10 mbar was applied andresidual oxide was drawn off for 2 h. The vacuum was broken with N₂ andthe product was decanted at 80° C. under N₂. 3 percent by weight ofAmbosol (silicate for neutralization) were added, and the mixture wasstirred at 100° C. and <10 Mbar for 3 h. The vacuum was broken with N₂and the reaction mixture was pressure-filtered through a Seitz K900filter. Analysis (mass spectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD)confirmed the mean composition C16C18-7 PO-10 EO—H.

Alkyl Ether Alcohol 6: C16C18-7 PO-4 EO—H by KOH Catalysis, Desalinated

Corresponds to surfactant of the general formula (II) R¹—O-13(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹=C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=4

A 2 L pressure autoclave with anchor stirrer was initially charged with308.7 g (1.21 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 4.0 g of 50% aqueous KOH solution (0.046 mol of KOH, 2.0 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,487 g (8.44 mol) of propylene oxide were metered in at 130° C. within 6h; P_(max) was 6.0 bar absolute. The mixture was stirred at 130° C. fora further 2 h. 211 g (4.8 mol) of ethylene oxide were metered in at 130°C. within 4 h; P_(max) was 5.0 bar absolute. The mixture was left toreact for 1 h until the pressure was constant, cooled down to 100° C.and decompressed to 1.0 bar absolute. A vacuum of <10 mbar was appliedand residual oxide was drawn off for 2 h. The vacuum was broken with N₂and the product was decanted at 80° C. under N₂. 3 percent by weight ofAmbosol (silicate for neutralization) were added, and the mixture wasstirred at 100° C. and <10 mbar for 3 h. The vacuum was broken with N₂and the reaction mixture was pressure-filtered through a Seitz K900filter. Analysis (mass spectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD)confirmed the mean composition C16C18-7 PO-4 EO—H.

Alkyl Ether Alcohol 7; C16C18C20 Guerbet-18 EO—H by KOH Catalysis,Desalinated

Corresponds to surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)-(CH₂CH₂O)_(z)—H withR¹=C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x=0, y=0 and z=18

A 2 L pressure autoclave with anchor stirrer was initially charged with261 g (1.01 mol) of C16C18C20 Guerbet alcohol and the stirrer wasswitched on. Thereafter, 4.2 g of 50% aqueous KOH solution (0.038 mol ofKOH, 2.1 g of KOH) were added, a reduced pressure of 25 mbar wasapplied, and the mixture was heated to 100° C. and kept there for 120min, in order to distill off the water. The mixture was purged threetimes with N₂. Thereafter, the vessel was tested for pressure retention,1.0 bar gauge (2.0 bar absolute) was set, the mixture was heated to 130°C. and then the pressure was set to 2.0 bar absolute. At 150 revolutionsper minute, 799 g (18.2 mol) of ethylene oxide were metered in at 130°C. within 14 h; P_(max) was 5.0 bar absolute. The mixture was left toreact for 1 h until the pressure was constant, cooled down to 100° C.and decompressed to 1.0 bar absolute. A vacuum of <10 mbar was appliedand residual oxide was drawn off for 2 h. The vacuum was broken with N₂and the product was decanted at 80° C. under N₂. 3 percent by weight ofAmbosol (silicate for neutralization) were added, and the mixture wasstirred at 100° C. and <10 mbar for 3 h. The vacuum was broken with N₂and the reaction mixture was pressure-filtered through a Seitz K900filter. Analysis (mass spectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD)confirmed the mean composition C16C18C20 Guerbet-18 EO—H.

Alkyl Ether Alcohol 8: C16C18C20 Guerbet-10 EO—H by KOH Catalysis,Desalinated

Corresponds to surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x=0, y=0 and z=10

A 2 L pressure autoclave with anchor stirrer was initially charged with396 g (1.53 mol) of C16C18C20 Guerbet alcohol and the stirrer wasswitched on. Thereafter, 4.17 g of 50% aqueous KOH solution (0.037 molof KOH, 2.1 g of KOH) were added, a reduced pressure of 25 mbar wasapplied, and the mixture was heated to 100° C. and kept there for 120min, in order to distill off the water. The mixture was purged threetimes with N₂. Thereafter, the vessel was tested for pressure retention,1.0 bar gauge (2.0 bar absolute) was set, the mixture- was heated to140° C. and then the pressure was set to 2.0 bar absolute. At 150revolutions per minute, 675 g (15.3 mol) of ethylene oxide were meteredin at 140° C. within 14 h; P_(max) was 5.0 bar absolute. The mixture wasleft to react for 1 h until the pressure was constant, cooled down to100° C. and decompressed to 1.0 bar absolute. A vacuum of <10 mbar wasapplied and residual oxide was drawn off for 2 h. The vacuum was brokenwith N₂ and the product was decanted at 80° C. under N₂. 3 percent byweight of Ambosol (silicate for netralization) were added, and themixture was stirred at 100° C. and <10 mbar for 3 h. The vacuum wasbroken with N₂ and the reaction mixture was pressure-filtered through aSeitz K900 filter. Analysis (mass spectrum, GPC, 1H NMR an CDCl₃, 1H NMRin MeOD) confirmed the mean composition C16C18C20 Guerbet-10 EO—H.

Alkyl Ether Alcohol 9: 2PH-14 EO-13 H by KOH Catalysis, Desalinated

Corresponds to surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹=C₁₀H₂₁,x=0, y=0 and z=14

A 2 L pressure autoclave with anchor stirrer was initially charged with234 g (1.5 mol) of 2-propytheptanol and the stirrer was switched on.Thereafter, 4,6 g of 50% aqueous KOH solution (0.041 mol of KOH, 2.3 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,924 g (21 mol) of ethylene oxide were metered in at 130° C. within 16 h;P_(max) was 6.0 bar absolute. The mixture was left to react fir 1 huntil the pressure was constant, cooled down to 100° C. and decompressedto 1.0 bar absolute. A vacuum of <10 mbar was applied and residual oxidewas drawn off for 2 h. The vacuum was broken with N₂ and the product wasdecanted at 80° C. under N₂. 3 percent by weight of Ambosol (silicatefor neutralization) were added, and the mixture was stirred at 100° C.and <10 mbar for 3 h. The vacuum was broken with N₂ and the reactionmixture was pressure-filtered through a Seitz K900 filter. Analysis(mass spectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD) confirmed the meancomposition 2PH-14 EO—H.

Alkyl Ether Alcohol 10: C16C18-7 PO-10 EO—H by KOH Catalysis, Basic

Corresponds to surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10

A 2 L pressure autoclave with anchor stirrer was initially charged with304 g (1.19 mol) of C16C18 alcohol and the stirrer was switched on.Thereafter, 4.13 g of 50% aqueous KOH solution (0.037 mol of KOH, 2.07 gof KOH) were added, a reduced pressure of 25 mbar was applied, and themixture was heated to 100° C. and kept there for 120 min, in order todistill off the water. The mixture was purged three times with N₂.Thereafter, the vessel was tested for pressure retention, 1.0 bar gauge(2.0 bar absolute) was set, the mixture was heated to 130° C. and thenthe pressure was set to 2.0 bar absolute. At 150 revolutions per minute,482 g (8.31 mol) of propylene oxide were metered in at 130° C. within 6h; P_(max) was 6.0 bar absolute. The mixture was stirred at 130° C. fora further 2 h. 522 g (11.9 mol) of ethylene oxide were metered in at130° C. within 10 h; P_(max) was 5.0 bar absolute. The mixture was leftto react for 1 h until the pressure was constant, cooled down to 100° C.and decompressed to 1.0 bar absolute. A vacuum of <10 mbar was appliedand residual oxide was drawn off for 2 h. The vacuum was broken with N₂and the product was decanted at 80° C. under N₂. Analysis (massspectrum, GPC, 1H NMR in CDCl₃, 1H NMR in MeOD) confirmed the meancomposition C16C18-7 PO-EO-13 H.

Preparation of the alkyl ether carboxylate (A)/alkyl ether alcohol (B)mixtures:

Abbreviations used:

-   EO ethyleneoxy-   PO propyleneoxy-   BuO 1,2-butyleneoxy

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 1 a):C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO—H by KOH Catalysis,Desalinated

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹=C₁₆H₃₃/C₁₈H₃₇, x=0, y=3 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with152.3 g (0.175 mol, 1.0 eq) of C16C18-3 PO-10 EO—H (from alkylalkoxylate 1 preparation example, KOH-catalyzed, desalinated) and 22.9 g(0.193 mol, 1.1 eq) of chloroacetic acid sodium salt, and the mixturewas stirred at 60° C. wider standard pressure at 400 revolutions perminute for 15 min. Thereafter, the following procedure was conductedeight times: 0.96 g (0.0240 mol, 0.1375 eq) of NaOH microprills(diameter 0.5-1.5 mm) was introduced, a vacuum of 30 mbar was applied toremove the water of reaction, the mixture was stirred for 50 min, andthen the vacuum was broken with N₂. A total of 7.7 g (0.193 mol, 1.1 eq)of NaOH microprills were added over a period of about 6.5 h. Over thefirst hour of this period, the speed of rotation was increased to about1000 revolutions per minute. Thereafter, stirring was continued at 60°C. and 30 mbar for 4 h. The vacuum was broken with N₂ and the experimentwas decanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 8.0. The water content was 0.9% at the end of thereaction (during the reaction the water content was: 0.8% before thesecond addition of NaOH, 0.9% before the third addition of NaOH, 1.3%before the fourth addition of NaOH, 1.1% before the fifth addition ofNaOH, 0.7% before the sixth addition of NaOH and 0.9% before the seventhaddition of NaOH). The NaCl content was determined via chloride analysisor 1H NMR with regard to the conversion rate of the chloroacetic acidsodium salt. By means of ¹H NMR in MeOD, the molar proportion ofchloroacetic acid sodium salt is determined (using the isolated signalat 3.92 to 3.94 ppm). It corresponds to about 0.01 eq of chloroaceticacid sodium salt. The proportion of NaCl is about 6.1% by weight(corresponding to ˜99 mol % of conversion of the organically boundchlorine to inorganic chloride). By NMR spectroscopy (¹H and ¹³C), thepresence of the desired surfactant mixture was continued and theproportion of secondary compounds was determined. Direct determinationof the carboxymethylation level from the ¹H NMR in MeOD is regrettablynot unambiguously possible since the alkyl ether carboxylate signal atabout 3.65-3.80 ppm overlaps with the signal for the diglycolic aciddisodium salt (protons on carbon atom directly adjacent to thecarboxylate group and to the oxygen atom in the ether function). Thecarboxyamethylation level was therefore determined as follows. By meansof ¹H NMR in MeOD, the molar proportion of glycolic acid sodium salt isdetermined (using the isolated signal at 3.82 to 3.84 ppm: protons oncarbon atom directly adjacent to the carboxylate group and to the oxygenatom in the ether function or the alcohol function). It corresponds toabout 0.05 eq of glycolic acid sodium salt. As the next step, the OHnumber of the reaction mixture is determined. It is 15.4 mg KOH/g. Theproportion that results from the OH group in the glycolic acid sodiumsalt has to be subtracted from this (about 2.7 mg KOH/g). This gives12.7 mg KOH/g as the corrected OH number. If the alkyl alkoxylate werestill present to an extent of 100%, the corrected OH number would be54.8 mg KOH/g (the alkyl alkoxylate—if it had not been depleted—wouldhave a proportion by weight of 85% in the reaction mixture). 12.7 isabout 23% of 54.8. Thus, the molar proportion of C16C18-3PO-10EO—H isabout 23 mol % (and the proportion of alkyl ether carboxylate about 77mol %). The carboxymethylation level is therefore about 77%. This isadditionally confirmed by a ¹³C NMR in MeOD. The signals therein fordiglycolic acid disodium salt and alkyl ether carboxylate are separatedfrom one another (signals for the carbon atoms of the carboxylate groupsat 177-178 ppm—signals can be distinguished from one another by spikingexperiments). Determination of the proportion of C16C18-3PO-10EO—H by ¹HTAI NMR in CDCl₃ (TAI is a shift reagent and stands for trichloroacetylisocyanate) is possible only to a limited degree, since the anionicalkyl ether carboxylate has poorer solubility in CDCl₃ than the nonionicalkyl alkoxylate.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 1 b):C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO—H by KOH Catalysis,Desalinated

An alternative preparation method to example 1a) is the use of aone-level toothed disk stirrer rather than a three-level beam stirrerand the use of a vacuum of about 150 mbar in combination with a nitrogenstream (rather than vacuum of 30 mbar). Otherwise, the reaction iseffected analogously to the manner described in 1a). Acarboxymethylation level of about 80% and a very similar spectrum ofsecondary components were achieved.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 2:C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO—H Comprising PotassiumAcetate and Water

A 250 mL flange reactor with a three-level beam stirrer was charged with174.0 g (0.20 mol, 1.0 eq) of C16C18-3 PO-10 EO—H mixed with 0.35 g ofpotassium acetate, 2.0 g of water and 26.2 g (0.220 mol, 1.1 eq) ofchloroacetic acid sodium salt, and the mixture was stirred at 60° C.under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 1.1 g(0.0275 mol, 0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) wereintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 min, and then the vacuum wasbroken with N₂. A total of 8.8 g (0.220 mol, 1.1 eq) of NaOH microprillswere added over a period of about 6.5 h. Over the first hour of thisperiod, the speed of rotation was increased to about 1000 revolutionsper minute. Thereafter, stirring was continued at 60° C. and 30 mbar for4 h. The vacuum was broken with N₂ and the experiment was decanted out(yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 8.5. The water content was 1.2%. Analysis waseffected analogously to the previous example. The molar proportion ofchloroacetic acid sodium salt is about 2 mol %. The NaCl content isabout 6.1% by weight. The OH number of the reaction mixture is 21.0 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 5 mol%. The carboxymethylation level is 72%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 3:C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO—H by KOH Catalysis, Basic

A 250 mL flange reactor with a three-level beam stirrer was charged with112.8 g (0.13 mol, 1.0 eq) of C16C18-3 PO- 10 EO—H comprising 0.004 molof C16C18-3 PO-10 EO—K (from Alkyl ether alcohol 3 preparation example,KOH-catalyzed, basic) and 17 g (0.143 mol, 1.1 eq) of chloroacetic acidsodium salt, and the mixture was stirred at 60° C. under standardpressure at 400 revolutions per minute for 15 min. Thereafter, thefollowing procedure was conducted eight times: 0.70 g (0.0174 mol,0.1338 eq) of NaOH microprills (diameter 0.5-1.5 mm) was introduced, avacuum of 30 mbar was applied to remove the water of reaction, themixture was stirred for 50 min, and then the vacuum was broken with N₂.A total of 5.56 g (0.139 mol, 1.07 eq) of NaOH microprills were addedover a period of about 6.5 h. Over the first hour of this period, thespeed of rotation was increased to about 1000 revolutions per minute.Thereafter, stirring was continued at 60° C. and 30 mbar for 4 h. Thevacuum was broken with N₂ and the experiment was decanted out (yield>95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 7. The water content was 1.0%. Analysis waseffected analogously to the previous example. The molar proportion ofchloroacetic acid sodium salt is about 1 mol %. The NaCl content isabout 6.1% by weight. The OH number of the reaction mixture is 16.7 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 4 mol%. The carboxymethylation level is 74%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 4:C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO—H by NaOH Catalysis, Basic

A 250 mL flange reactor with a three-level beam stirrer was charged with161.8 g (0.186 mol, 1.0 eq) of C16C18-3 PO-10 EO—H comprising 0.008 molof C16C18-3 PO-10 EO—Na (from Alkyl alkoxylate 4 preparation example,NaOH-catalyzed, basic) and 24.4 g (0.205 mol, 1.1 eq) of chloroaceticacid sodium salt, and the mixture was stirred at 60° C. under standardpressure at 400 revolutions per minute for 15 min. Thereafter, thefollowing procedure was conducted eight times: 0.99 g (0.0246 mol,0.1324 eq) of NaOH microprills (diameter 0.5-1.5 mm) was introduced, avacuum of 30 mbar was applied to remove the water of reaction, themixture was stirred for 50 min, and then the vacuum was broken with N₂.A total of 7.88 g (0.197 mol, 1.06 eq) of NaOH microprills were addedover a period of about 6.5 h. Over the first hour of this period, thespeed of rotation was increased to about 1000 revolutions per minute.Thereafter, stirring was continued at 60° C. and 30 mbar for 4 h. Thevacuum was broken with N₂ and the experiment was decanted out (yield>95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 7. The war content was 0.9%. Analysis was effectedanalogously to the previous example. The molar proportion ofchloroacetic acid sodium salt is about 1 mol %. The NaCl content isabout 6.1% by weight. The OH nuMber of the reaction mixture is 15.4 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 3 mol%. The carboxymethylation level is 75%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 5:C16C18-7PO-10EO—CH₂CO₂Na/C16C18-7 PO-10 EO—H by KOH Catalysis,Desalinated

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)-(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with143.3 g (0.130 mol, 1.0 eq) of C16C18-7 PO-10 EO—H (from Alkylalkoxylate 5 preparation example, KOH-catalyzed, desalinated) and 17.0 g(0.143 mol, 1.1 eq) of chloroacetic acid sodium salt, and the mixturewas stirred at 45° C. under standard pressure at 400 revolutions perminute for 15 min. Thereafter, the following procedure was conductedeight times: 0.72 g (0.0179 mol, 0.1375 eq) of NaOH microprills(diameter 0.5-1.5 mm) was introduced, a vacuum of 30 mbar was applied toremove the water of reaction, the mixture was stirred for 50 min, andthen the vacuum was broken with N₂. A total of 5.72 g (0.143 mol, 1.1eq) of NaOH microprills were added over a period of about 6.5 h. Overthe first hour of this period, the speed of rotation was increased toabout 1000 revolutions per minute. Thereafter, stirring was continued at45° C. and 30 mbar for 4 h. The vacuum was broken with N₂ and theexperiment was decanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 8.5. The water content was 1.5%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 44.6 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 5 mol %. The NaCl content isabout 4.8% by weight. The OH number of the reaction mixture is 16.2 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 5 mol%. The carboxymethylation level is 70%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol mixture 6:C16C18-7PO-4EO—CH₂CO₂Na/C16C18-7 PO-4 EO—H by KOH Catalysis, Desalinated

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR₁═C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=4, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with127.5 g (0.15 mol, 1.0 eq) of C16C18-7 PO—H (from Alkyl alkoxylate 6preparation example, KOH-catalyzed, desalinated) and 19.6 g (0.165 mol,1.1 eq) of chloroacetic acid sodium salt, and the mixture was stirred at60° C. under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 0.83 g(0.0206 mol, 0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) wasintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 mm, and then the vacuum wasbroken with N₂. A total of 6.6 g (0.165 mol, 1.1 eq) of NaOH microprillswere added over a period of about 6.5 h. Over the first hour of thisperiod, the speed of rotation was increased to about 1000 revolutionsper minute. Thereafter, stirring was continued at 60° C. and 30 mbar for4 h. The vacuum was broken with N₂ and the experiment was decanted out(yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 8.5. The water content was 0.9%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 56.5 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 1 mol %. The NaCl content isabout 6.4% by weight. The OH number of the reaction mixture is 23.2 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 2 mol%. The carboxymethylation level is 61%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 7:C16C18C20-Guerbet-18EO—CH₂CO₂Na/C16C18C20-Guerbet-18 EO—H by KOHCatalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)-(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x=0, y=0 and z=18, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with159.3 g (0.150 mol, 1.0 eq) of C16C18C20-Guerbet-18 EO—H comprising0.006 mol of C16C18C20-Guerbet-18 EO—K (analogous to Alkyl alkoxylate 7preparation example, except that no desalination was undertaken and thealkoxylate remained basic) and 19.6 g (0.165 mol, 1.1 eq) ofchloroacetic acid sodium salt, and the mixture was stirred at 45° C.Under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 0.80 g(0.0199 mol, 0.1325 eq) of NaOH microprills (diameter 0.5-1.5 mm) wasintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 min, and then the vacuum wasbroken with N₂. A total of 6.36 g (0.159 mol, 1.06 eq) of NaOHmicroprills were added over a period of about 6.5 h. Over the first hourof this period, the speed of rotation was increased to about 1000revolutions per minute. Thereafter, stirring was continued at 45° C. and30 mbar for 4 h. The vacuum was broken with N₂ and the experiment wasdecanted out (yield >95%).

This gave a solid which was white-yellowish at 20° C. The pH (5% inwater) was 7. The water content was 1.4%. Analysis was effectedanalogously to the previous example (taking account of the highermolecular weight, at 0% conversion, there would be an OH number of 46.2mg KOH/g for the reaction mixture). The molar proportion of chloroaceticacid sodium salt is about 5 mol %. The NaCl content is about 5.1% byweight. The OH number of the reaction mixture is 10.2 mg KOH/g. Themolar proportion of glycolic acid sodium salt is about 8 mol %. Thecarboxymethylation level is 87%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 8:C16C18C20-Guerbet-10EO—CH₂CO₂Na/C16C18C20-Guerbet-10 EO—H by KOHCatalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₁C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x=0, y=0 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with142.0 g (0.200 mol, 1.0 eq) of C16C18C20-Guerbet-10 EO—H (from Alkylalkoxylate 8 preparation example) and 26.2 g (0.22 mol 1.1 eq) ofchloroacetic acid sodium salt, and the mixture was stirred at 45° C.under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 1.1 g(0.0275 mol, 0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) wereintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 min, and then the vacuum wasbroken with N₂. A total of 8.8 g (0.22 mol, 1.1 eq) of NaOH microprillswere added over a period of about 6.5 h. Over the first hour of thisperiod, the speed of rotation was increased to about 1000 revolutionsper minute. Thereafter, stirring was continued at 45° C. and 30 mbar for4 h. The vacuum was broken with N₂ and the experiment was decanted out(yield >95%).

This gave a solid which was white-yellowish at 20° C. The pH (5% inwater) was 7. The water content was 1.5%. Analysis was effectedanalogously to the previous example (taking account of the highermolecular weight, at 0% conversion, there would be an OH number of 64.9mg KOH/g for the read mixture). The molar proportion of chloroaceticacid sodium salt is about 2 mol %. The NaCl content is about 7.3% byweight. The OH number of the reaction mixture is 10.8 mg KOH/g. Themolar proportion of glycolic acid sodium salt is about 2 mol %. Thecarboxymethylation level is 85%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 9:2PH-14EO—CH₂CO₂Na/2PH-14 EO—H by KOH Catalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹═C₁₀H₂₁,x=0, y=0 and z=14, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with160.9 g (0.208 mol, 1.0 eq) of 2PH-14 EO—H comprising 0.006 mol of2PH-14 EO—K (analogous to Alkyl alkoxylate 9 preparation example, exceptthat no desalination was undertaken and the alkoxylate remained basic)and 27.2 g (0.229 mol, 1.1 eq) of chloroacetic acid sodium salt, and themixture was stirred at 60° C. under standard pressure at 400 revolutionsper minute for 15 min. Thereafter, the following procedure was conductedeight times: 1.12 g (0.0279 mol, 0.1340 eq) of NaOH microprills(diameter 0.5-1.5 mm) were introduced, a vacuum of 30 mbar was appliedto remove the water of reaction, the mixture was stirred for 50 min, andthen the vacuum was broken with N₂. A total of 8.92 g (0.223 mol, 1.07eq) of NaOH microprills were added over a period of about 6.5 h. Overthe first hour of this period, the speed of rotation was increased toabout 1000 revolutions per minute. Thereafter, stirring was continued at60° C. and 30 mbar for 4 h. The vacuum was broken with N₂ and theexperiment was decanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 7. The water content was 1.1%. Analysis waseffected analogously to the previous example (taking account of thelower molecular weight, at 0% conversion, there would be an OH number of60.5 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 1 mol %. The NaCl content isabout 6.8% by weight. The OH number of the reaction mixture is 19.2 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 12 mol%. The carboxyrnethylation level is 79%.

Comparative Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture C10(Noninventive, too Low a Molar Ratio of (A) to (B)):C16C18-3PO-10EO—CH₂CO₂Na/C16C18-3 PO-10 EO-—H Comprising PotassiumAcetate in a Ratio of 30 mol %:70 mol %

A 250 mL flange reactor with a three-level beam stirrer was charged with130.2 g (0.15 mol, 1.0 eq) of C16C18-3 PO-10 EO—H mixed with 0.26 g ofpotassium acetate and 19.6 g (0.165 mol, 1.1 eq) of chloroacetic acidsodium salt, and the mixture was stirred at 60° C. under standardpressure at 400 revolutions per minute for 15 min. Thereafter, thefollowing procedure was conducted eight times: 0.83 g (0.0206 mol,0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) was introduced, avacuum of 30 mbar was applied to remove the water of reaction, themixture was stirred for 50 min, and then the vacuum was broken with N₂.A total of 6.6 g (0.165 mol, 1.1 eq) of NaOH microprills were added overa period of about 6.5 h. Over the first hour of this period, the speedof rotation was increased to about 1000 revolutions per minute.Thereafter, stirring was continued at 60° C. and 30 mbar for 4 h. Thevacuum was broken with N₂ and the experiment was decanted out (yield>95%).

This gave a liquid which was brownish and viscous at 20° C. The pH (5%in water) was 11. The water content was 0.9%. Analysis was effectedanalogously to the previous example. The molar proportion ofchloroacetic acid sodium salt is about 38 mol %. The NaCl content isabout 4.4% by weight. The OH number of the reaction mixture is 52.6 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 2 mol%. The carboxymethylation level is 30%.

Comparative alkyl ether carboxylate/alkyl ether alcohol mixture C11(noninventive, too high a molar ratio of (A) to (B)):C16C18-3PO-10EO—CH₂CO₂Na:C16C18-3 PO-10 EO—H in a ratio of 95 mol %: 5mol %

A 250 mL flange reactor with a three-level beam stirrer was charged with173.6 g (0.20 mol, 1.0 eq) of C16C18-3 PO-10 EO—H (from Alkyl alkoxylate1 preparation example, KOH-catalyzed, desalinated) and 47.5 g (0.40 mol,2.0 eq) of chloroacetic acid sodium salt, and the mixture was stirred at50° C. under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 2 g (0.05mol, 0.25 eq) of NaOH microprills (diameter 0.5-1.5 mm) were introduced,a vacuum of 30 mbar was applied to remove the water of reaction, themixture was stirred for 50 min, and then the vacuum was broken with N₂.A total of 16 g (0.40 mol, 2 eq) of NaOH microprills were added over aperiod of about 6.5 h. Over the first hour of this period, the speed ofrotation was increased to about 1000 revolutions per minute. Thereafter,stirring was continued at 50° C. and 30 mbar for 10 h. The vacuum wasbroken with N₂ and the entire experiment was transferred into a 1000 mlround-neck flask.

At 70° C., 350 mL of water and 150 g of 1-pentanol were added whilestirring. The pH was adjusted from pH=12 to pH=2. by means of 41.3 g of32% aqueous HCl solution. The mixture was heated to 90° C. and stirredfor another 1 h. Subsequently, the mixture was transferred immediatelyinto a separating funnel and the hot phases were separated from oneanother. The aqueous phase comprising NaCl and other by-products wasdiscarded. The organic phase (comprising alkyl ether carboxylic acid andalkyl alkoxylate) was removed and the 1-pentanol was removed at 100° C.and <10 mbar. In a 500 mL round-neck flask, the alkyl ether carboxylicacid/alkyl ether alcohol mixture was admixed at 75° C. with 50% aqueousNaOH solution while stirring, so as to result in a pH of pH=7.

According to ¹H NMR in MeOD and ¹H TAI NMR in CDCl₃, thecarboxymethylation level is about 89%, and so 11 mol % of alkylalkoxylate is present. This mixture was subjected to a furthercarboxymethylation.

In a 250 mL flange reactor with three-level beam stirrer, 75 g(comprising 0.1 mol of alkyl alkoxylate, 1.0 eq) of the alkyl ethercarboxylate/alkyl ether alcohol mixture (comprising 11 mol % of alkylether alcohol) were stirred at 50° C. and 30 mbar for 30 min. After thevacuum had been broken with nitrogen, 2.33 g (0.02 mol, 2.0 eq) ofchloroacetic acid sodium salt were added and the mixture was stirred at50° C. under standard pressure at 400 revolutions per minute for 1.5min. Thereafter, the following procedure was conducted eight times: 0.1g (0.0025 mol, 0.25 eq) of NaOH microprills (diameter 0.5-1.5 mm) wasintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture stirred for 50 min, and then the vacuum was brokenwith N₂. A total of 0.8 g (0.02 mol, 2 eq) of NaOH microprills was addedover a period of about 6.5 h. Over the first hour of this period, thespeed of rotation was increased to about 1000 revolutions per minute.Thereafter, stirring was continued at 50° C. and 30 mbar for 10 h, Thevacuum was broken with N₂ and the entire experiment was transferred intoa 500 ml round-neck flask.

At 60° C., 110 g of water and 110 g of 1-pentanol were added whilestirring. The pH was adjusted from pH=11 to pH=3 by means of 32% aqueousHCl solution. The mixture was heated to 90° C. and stirred for another 1h. Subsequently, the mixture was transferred immediately into aseparating funnel and the hot phases were separated from one another.The aqueous phase comprising NaCl and other by-products was discarded.The organic phase (comprising alkyl ether carboxylic acid and alkylether alcohol) was removed and the 1-pentanol was removed at 100° C. and<10 mbar. In a 250 round-neck flask, the alkyl ether carboxylicacid/alkyl ether alcohol mixture was admixed at 60° C. with 50% aqueousNaOH solution while stirring, so as to result in a pH of pH=7.

According to ¹H NMR in MeOD and ¹H TAI NMR in CDCl₃, thecarboxymethylation level was about 95%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 12:C16C18-7PO-10EO—CH₂CO₂Na/C16C18-7 PO-10 EO—H by KOH Catalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with165.3 g (0.150 mol, 1.0 eq) of C16C18-7 PO-10 EO—H comprising 0.005 molof C16C18-7 PO-10 EO—K (from Alkyl alkoxylate 10 preparation example,KOH-catalyzed, basic) and 19.6 g (0.165 mol, 1.1 eq) of chloroaceticacid sodium salt (98% purity), and the mixture was stirred at 45° C.under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 0.83 g(0.0206 mol, 0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) wasintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 min, and then the vacuum wasbroken with N₂. A total of 6.6 g (0.165 mol, 1.1 eq) of NaOH microprillswere added over a period of about 6.5 h. Over the first hour of thisperiod, the speed of rotation was increased to about 1000 revolutionsper minute. Thereafter, stirring was continued at 45° C. and 30 mbar for4 h. The vacuum was broken with N₂ and the experiment was decanted out(yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 7.5. The water content was 1.3%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 44.6 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 2 mol %. The NaCl content isabout 4.8% by weight. The OH number of the reaction mixture is 10.4 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 5 mol%. The carboxymethylation level is 81%.

Alkyl Ether Carhoxylate/Alkyl Ether Alcohol Mixture 13:C16C18-7PO-10EO—CH₂CO₂Na/C16C18-7 PO-10 EO—H by KOH Catalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)₂—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with165.3 g (0.150 mol, 1.0 eq) of C16C18-7 PO-10 EO—H comprising 0.005 molof C16C18-7 PO-10 EO—K (from Alkyl alkoxylate 10 preparation example,KOH-catalyzed, basic) and 19.6 g (0.165 mol, 1.1 eq) of chloroaceticacid sodium salt (98% purity), and the mixture was stirred at 45° C.under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 0.83 g(0.0206 mol, 0.1375 eq) of NaOH microprills (diameter 0.5-1.5 mm) wasintroduced, a gentle N2 stream and vacuum of ˜100 mbar was applied toremove the water of reaction, the mixture was stirred for 50 min, andthen the vacuum was broken with N₂. A total of 6.6 g (0.165 mol, 1.1 eq)of NaOH rnicroprills were added over a period of about 6.5 h. Over thefirst hour of this period, the speed of rotation was increased to about1000 revolutions per minute. Thereafter, stirring was continued at 45°C. and at ˜100 mbar with a gentle N2 stream for 3 h. The vacuum wasbroken with N₂ and the experiment was decanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 11.2. The water content was 1.3%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 44.6 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 3 mol %. The NaCl content isabout 4.8% by weight. The OH number of the reaction mixture is 12.4 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 2 mol%. The carboxymethylation level is 73%.

For the further use tests, the pH was adjusted to a range of 6-8 byaddition of a little aqueous hydrochloric acid.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 14:C16C18-7PO-10EO—CH₂CO₂Na/C6C18-7 PO-10 EO—H by KOH Catalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹=C₁₆H₃₃/C₁₈H₃₇, x=0, y=7 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with165.3 g (0.150 mol, 1.0 eq) of C16C18-7 PO-10 EO—H comprising 0.005 molof C16C18-7 PO-10 EO—K (from Alkyl alkoxylate 10 preparation example,KOH-catalyzed, basic) and 24.1 g (0.203 mol, 1.35 eq) of chloroaceticacid sodium salt (98% purity), and the mixture was stirred at 45° C.under standard pressure at 400 revolutions per minute for 15 min.Thereafter, the following procedure was conducted eight times: 1.02 g(0.0253 mol, 0.1688 eq) of NaOH microprills (diameter 0.5-1.5 mm) wereintroduced, a vacuum of 30 mbar was applied to remove the water ofreaction, the mixture was stirred for 50 min, and then the vacuum wasbroken with N₂. A total of 8.1 g (0.203 mol, 1.35 eq) of NaOHmicroprills were added over a period of about 6.5 h. Over the first hourof this period, the speed of rotation was increased to about 1000revolutions per minute. Thereafter, stirring was continued at 45° C. andat 30 mbar for 3 h. The vacuum was broken with N₂ and the experiment wasdecanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 7.5. The water content was 1.5%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 43.4 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 2 mol %. The NaCl content isabout 6.0% by weight. The OH number of the reaction mixture is 8.0 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 3 mol%. The carboxymethylation level is 85%.

Alkyl Ether Carboxylate/Alkyl Ether Alcohol Mixture 15:C16C18-7PO-10EO—CH₂CO₂Na/C16C18-7 PO-10 EO—H by KOH Catalysis, Basic

Corresponds to surfactant mixture of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M andsurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H withR¹═C₁₆H₃₃/C₁₈ H₃₇, x=0, y=7 and z=10, M=Na.

A 250 mL flange reactor with a three-level beam stirrer was charged with165.3 g (0.150 mol, 1.0 eq) of C16C18-7 PO-10 EO—H comprising 0.005 molof C16C18-7 PO-10EO—K (from Alkyl alkoxylate 10 preparation example,KOH-catalyzed, basic) and 12 g (0.150 mol, 1.0 eq) of aqueous 50% NaOH,and the mixture was stirred under standard pressure at 400 revolutionsper minute. The mixture was heated to 80° C. and the water of reactionwas removed at 30 mbar and 1.5 L of N₂/h for 8 h. Over the first hour ofthis period, the speed of rotation was increased to about 1000revolutions per minute. The water content was 0.35%.

Then 19.6 g (0.165 mol 1.1 eq) of chloroacetic acid sodium salt (98%purity) were added in portions at 80° C., 30 mbar and 1.5 L of N₂/hwithin 7 h. Thereafter, stirring, was continued at 80° C. and at 30 mbarand 1.5 L of N₂/h for 4 h. The vacuum was broken with N₂ and theexperiment was decanted out (yield >95%).

This gave a liquid which was white-yellowish and viscous at 20° C. ThepH (5% in water) was 9.6. The water content was 0.2%. Analysis waseffected analogously to the previous example (taking account of thehigher molecular weight, at 0% conversion, there would be an OH numberof 44.6 mg KOH/g for the reaction mixture). The molar proportion ofchloroacetic acid sodium salt is about 1 mol %. The NaCl content isabout 4.8% by weight. The OH number of the reaction mixture is 13.3 mgKOH/g. The molar proportion of glycolic acid sodium salt is about 12 mol%. The carboxymethylation level is 83%.

If required, after dilution with butyl diethylene glycol and water, itwas possible to adjust the pH to pH=7.75 with the aid of aqueoushydrochloric acid.

Commentary on the preparation of the alkyl ether carboxylate (A)/alkylether alcohol (B) mixtures:

As can be seen in the above examples of mixtures 1 to 15 (excluding C10and C11) from the respective carboxymethylation level, given efficientuse of carboxymethylation reagent (e.g. <1.3 eq of ClCH₂CO₂Na;otherwise, a large amount of secondary components which are notbeneficial for the later use are produced), it is more difficult toachieve carboxymethylation levels of >84% with increasing number ofpropyleneoxy units present in the nonionic surfactant (B) of the generalformula (II), given the same ethoxylation level: for examplecarboxymethylation level 85% in mixture 8 (based onC16C18C20-Guerbet-10EO) compared to carboxymethylation level 75% inmixture 4 (based on C16C18-3PO-10EO) compared to carboxymethylationlevel 70% in mixture 5 (based on C16C18-7PO-10EO). This was unexpected.

Very high carboxymethylation levels of 95%, for example, were possibleonly via a reaction conducted twice (which is thus costly andinconvenient) (see comparative mixture C11). In addition, it wasnecessary to use very high excesses of chloroacetic acid sodium salt(e.g. 2.0 eq). The surfactant here was based again on C16C18-3PO-10EO.

It was found that, surprisingly, the presence of neutralizedalkoxylation catalyst, for example KOAc, disrupts the cartoxymethylation (see comparative mixture C10). In spite of otherwisesimilar reaction conditions, the carboxymethylation level was only 30%(C10), whereas it was 77% in mixture 1a) (each surfactant based onC16C18-3PO-10EO).

An unexpected approach to a solution in the presence of KOAc (which canbe removed only with difficulty) is demonstrated by mixture 2. In thatcase, a little water was added at the start of the carboxymethylation,and a better carboxymethylation level of 72% was achieved again as aresult.

A much simpler and novel approach (because it avoids the neutralizationstep or a removal of salts at the end of each alkoxylation) is the useof basic alkoxylate in the carboxymethylation. Mixtures 3 and 4 showcarboxymethylation levels of 74% and 75% respectively. The surfactanthere was based again on C16C18-3PO-10EO. The amount of base introducedvia the alkoxylate was included in the calculation and the amount ofNaOH microprills was reduced correspondingly. When desalinated materialwas used, the carboxymethylation level was 77% (mixture 1a)).

Mixture 1b) shows the surprisingly positive influence of a toothed diskstirrer, in this way, it was possible to increase the carboxymethylationlevel from 77% to about 80% compared to mixture 1a). As is surprisinglyobserved for alkyl ether carboxylate/alkyl ether alcohol mixture 12 or13 compared to alkyl ether carboxylate/alkyl ether alcohol mixture 5, asmall excess of base (sum total of basic alkoxylate and NaOHmicroprills) compared to the chloroacetic acid sodium salt isadvantageous, since a higher value for the carboxymethylation level at81% (mixture 12) or 73% (mixture 13) can be achieved than for mixture 5(carboxymethylation level 70%). The differences between mixtures 12 and13 relating to the carboxymethylation level can be explained by thesmaller reduction in pressure during the reaction. However, in anindustrial scale process, very low pressures of <20 mbar can be achievedonly with a very high level of cost and inconvenience (for example witha higher-performance and hence more energy-intensive or costly pump).Therefore, the carboxymethylation level of 73% compared to 70%constitutes an improvement because it is additionally easier to achievein an industrial scale process. An increase in the carboxymethylationlevel to 85% by increasing the eq of chloroacetic acid sodium salt andNaOH is shown by mixture 14. Mixture 15 shows an alternative method forproducing the desired surfactant mixture, wherein the water of reactionthat forms is depleted before chloroacetic acid sodium salt is added inorder to reduce the hydrolysis of the carboxymethylation reagent.

In tests which follow (e,g. table 1), a further advantage of the methodis additionally demonstrated. No costly and inconvenient removal of NaClfrom the above mixtures is required. Therefore, there is no need for theadditional steps in the literature such as acidification, phaseseparation and re-neutralization of the alkyl ether carboxylic acid.

Testing of the alkyl ether carboxylate (A)/alkyl ether alcohol (B)mixtures:

Test methods:

Determination of Stability

The stability of the concentrates of the alkyl ether carboxylate(A)/alkyl ether alcohol (B) mixtures was determined by visual assessmentafter storage at appropriate temperatures for 2 weeks. The concentratescomprised water and butyl diethylene glycol, and also the alkyl ethercarboxylate (A)/alkyl ether alcohol (B) mixtures described in thepreparation examples (if required, the pH was adjusted to a range from6.5 to 8 by addition of aqueous hydrochloric acid). Notice was taken asto whether the concentrates remain homogeneous or whether significantphase separations which prevent homogeneous sampling arise. In addition,the concentrates (where possible) were frozen at −18° C. and thawedagain at 20° C., and an observation was made as to whether anirreversible phase separation arises.

Determination of Viscosity

The dynamic viscosities of the concentrates of the alkyl ethercarboxylate (A)/alkyl ether alcohol (B) mixtures were determined with anAnton Parr RheolabQC viscometer. The concentrates comprised water andbutyl diethylene glycol (BDG), and also the ether carboxylate (A)/alkylether alcohol (B) mixtures described in the preparation examples. Theviscosities were conducted at shear rates of 10, 100, 250 and(optionally) 1000 s⁻¹ and temperatures of (optionally 5) 20 and 50° C.

Determination of Solubility

The surfactants in the concentration to be examined in each case insaline water with the particular salt composition were stirred at 20-30°C. for 30 min (alternatively, the surfactant was dissolved in water, thepH was adjusted if required to a range from 6.5 to 8 by addition ofaqueous hydrochloric acid, and appropriate amounts of the particularsalt were dissolved therein at 20° C.). Thereafter, the mixture washeated stepwise until turbidity or a phase separation set in. This wasfollowed by cautious cooling, and the point at which the solution becameclear or scattering became slight again was noted. This was recorded asthe cloud point. At particular fixed temperatures, the appearance of thesurfactant solution in saline water was noted. Clear solutions orsolutions which have slight scatter and become somewhat lighter in coloragain through gentle shear (but do not foam with time) are regarded asacceptable. Said slightly scattering surfactant solutions were filteredthrough a filter having pore size 2 μm. No removal at all was found.

Determination of Interfacial Tension

Interfacial tensions of crude oil with respect to saline water weredetermined in the presence of the surfactant solution at a temperatureby the spinning drop method on an SVT20 from DataPhysics. For thispurpose, an oil droplet was injected into a capillary filled with salinesurfactant solution at temperature and the expansion of the droplet atapproximately 4500 revolutions per minute was observed and the evolutionof the interfacial tension with time was noted. The interfacial tensionIFT (or s₁₁) is calculated—as described by Hans-Dieter Dörfler in“Grenzflächen and kolloid-disperse Systeme” [Interfaces and ColloidallyDisperse Systems], Springer Verlag Berlin Heidelberg 2002—by thefollowing formula from the cylinder diameter d_(z), the speed ofrotation w, and the density differential:

(d ₁ −d ₂): s ₁₁=0.25·d _(z) ³ ·w2·(d ₁ −d ₂).

The API gravity (American Petroleum Institute gravity) is a conventionalunit of density commonly used in the USA for crude oils. It is usedglobally for characterization and as a quality standard for crude oil.The API gravity is calculated from the relative density P_(rel) of thecrude oil at 60° F. (15.56° C.), based on water, using

API gravity=(141.5 /P_(rel)−)131.5.

Test Results:

The following test results were achieved:

The test results for stability and viscosity of the concentrates areshown in table 1.

TABLE 1 Concentrates of alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture Viscosity at Viscosity at Appearance Appearance 20°C. and 50° C. and after storage at after freezing different different20° C. for two and later Example Surfactant concentrate shear ratesshear rates weeks thawing at 20° C. 1 40% by weight of alkyl 65 (JAIP =25 (JAIP = Liquid with Liquid with ether carboxylate/alkyl 100 Hz). 100Hz). very small small amount of ether alcohol mixture 1 amount ofhomogeneously b) [comprising homogeneously distributed surfactantmixture of distributed crystals, which C16C18-3PO-10EO- crystals, whichdissolve after CH₂CO₂Na:C16C18- dissolve after heating to 50° C.3PO-10EO-H (80 heating to 50° C. (homogeneous mol %:20 mol %)]^(a)), 30%(homogeneous metered by weight of BDG, 30% metered addition of the byweight of water addition of the concentrate in concentrate in saltsolution at salt solution at 20° C. and 20° C. and complete completedissolution in dissolution in salt solution salt solution with totalwith total salinity 30 000 salinity 30 000 ppm) ppm) 2 60% by weight ofalkyl ~340 mPas ~110 mPas Liquid with Liquid with ethercarboxylate/alkyl (10 Hz) (10 Hz) small amount of small amount of etheralcohol mixture 5 340 (JAIP = ~100 mPas homogeneously homogeneously[comprising surfactant 100 Hz). (100 Hz) distributed distributed mixtureof C16C18- 310 (JAIP = ~100 mPas crystals, which crystals, which7PO-10EO- 1000 Hz). (1000 Hz) dissolve after dissolve afterCH₂CO₂Na:C16C18- heating to heating to 50° C. 7PO-10EO-H (70 50° C.(homogeneous mol %:30 mol %)]^(b)), (homogeneous metered 20% by weightof BDG, metered addition of the 20% by weight of water addition of theconcentrate in concentrate in salt solution at salt solution at 20° C.and 20° C. and complete complete dissolution in dissolution in saltsolution salt solution with total with total salinity 30 000 salinity 30000 ppm) ppm) 3 40% by weight of alkyl 55 (JAIP = 25 (JAIP = Liquid withLiquid with ether carboxylate/alkyl 100 Hz). 100 Hz). small amount ofsmall amount of ether alcohol mixture 6 homogeneously homogeneously[comprising surfactant distributed distributed mixture of C16C18-crystals, which crystals, which 7PO-4EO- dissolve after dissolve afterCH₂CO₂Na:C16C18- heating to 50° C. heating to 50° C. 4PO-10EO-H (61(homogeneous (homogeneous mol %:39 mol %)]^(c)), 30% metered metered byweight of BDG, 30% addition of the addition of the by weight of waterconcentrate in concentrate in salt solution at salt solution at 20° C.and 20° C. and complete complete dissolution in dissolution in saltsolution salt solution with total with total salinity 30 000 salinity 30000 ppm) ppm) 4 60% by weight of alkyl ~260 mPas ~60 mPas Clear liquidClear liquid ether carboxylate/alkyl (10 Hz) (10 hz) (homogeneous(homogeneous ether alcohol mixture 7 ~260 mPas ~67 mPas metered metered[comprising surfactant (100 Hz) (100 Hz) addition of the addition of themixture of C16C18C20- ~240 mPas ~71 mPas concentrate in concentrate inGuerbet-18EO- (1000 Hz) (1000 Hz) salt solution at salt solution atCH₂CO₂Na:C16C18C20- 20° C. and 20° C. and Guerbet-18EO-H (87 completecomplete mol %:13 mol %)]^(e)), 20% dissolution in dissolution in byweight of BDG, 20% salt solution salt solution by weight of water withtotal with total salinity 30 000 salinity 30 000 ppm) ppm) 5 40% byweight of alkyl 70 (JAIP = ~30 mPas Clear liquid Freezing not ethercarboxylate/alkyl 100 Hz). (100 Hz) (homogeneous possible ether alcoholmixture 7 metered at −18° C.; [comprising surfactant addition of thestill a clear mixture of C16C18C20- concentrate in liquid afterGuerbet-18EO- salt solution at storage at −18° C. CH₂CO₂Na:C16C18C20-20° C. and for 2 weeks Guerbet-18EO-H (87 complete mol %:13 mol%)]^(e)), 30% dissolution in by weight of BDG, 30% salt solution byweight of water with total salinity 30 000 ppm) ^(a))alkyl ethercarboxylate/alkyl ether alcohol mixture 1 b); corresponds to surfactantmixture of 80 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 20 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—((CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na. ^(b))alkyl ethercarboxylate/alkyl ether alcohol mixture 5); corresponds to surfactantmixture of 70 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 30 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na. ^(c))alkyl ethercarboxylate/alkyl ether alcohol mixture 6); corresponds to surfactantmixture of 61 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 39 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 4, M = Na. d) alkyl ethercarboxylate/alkyl ether alcohol mixture 8); corresponds to surfactantmixture of 85 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 15 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x = 0, y = 0 and z = 10, M = Na. ^(e))alkyl ethercarboxylate/alkyl ether alcohol mixture 7); corresponds to surfactantmixture of 87 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 13 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x = 0, y = 0 and z = 18, M = Na.

As can be seen in table 1 from examples 1 to 4, it is possible to obtainconcentrates with active content about 55% (surfactant mixture) whichremain stable in spite of the presence of ≥3% by weight of NaCl (fromalkyl ether carboxylate/akyl ether alcohol mixture): no phase separationoccurs because of the presence of electrolytes. As a result, there is noneed for the step for complex removal of NaCl by phase separation (forexample acidification, heating to 90° C., phase separation optionallywith solvent, neutralize organic phase again; see also alkyl ethercarboxylate/alkyl alkoxylate mixture 11) in the alkyl ether carboxylatepreparation. This means quicker production, lower consumption ofchemicals, lower energy expenditure and lower costs. In addition, nowaste water with a high salt content is sent to the surface water (via awater treatment plant). Instead, the NaCl from the preparation is pumpedinto the mineral oil deposit as well. In the deposit, it encounterssalty formation water having an enormously large excess of NaCl relativeto the volume pumped in.

The transport of these concentrates (from the manufacturing site to thedeposit) causes less pollution of the environment, since the proportionof unnecessarily transported water is low (not 70% by weight of water asin many anionic surfactant solutions but merely, for example, 20-30% byweight) and hence less space and energy is consumed. Because of thelarge volumes (for example 10,000 to of surfactant per annum) for thedevelopment of a field over 10 years, expenditure on containerinsulation or moderate heating is also worthwhile in order to keep theconcentrate at about 15-20° C., since a very large amount of energy issaved on the transport side (lower diesel consumption in ships andtrucks).

As shown in example 5, the concentrate from example 4 can be diluted byaddition of equal amounts of BDG and water to arrive at concentrateswhich have very good cold stability (at −18° C., the concentrate forexample 5 is still liquid) and can be handled more easily in the deposit(less intensive heating measures; dilution measures on site arepossible, since water and BDG can be provided separately or isavailable).

Said concentrates from examples 1 to 5 are easy to marine in the field,since their viscosities are below 1000 mPas at 50° C. (even at low shearrates of 10 Hz) and therefore do not present any difficulties in thepumps used.

Even the relatively small amounts of homogeneously distributed crystalsobserved in some concentrates are unproblematic, since they dissolve asa result of brief heating to 50° C. Alternatively, the concentrate canbe pumped homogeneously into the injection water together with thecrystals, the concentrate and the crystals dissolving immediately.

The test results for solubility and for interfacial tension after 3 hare shown in table 2.

TABLE 2 Interfacial tensions with alkyl ether carboxylate/alkyl etheralcohol surfactant mixture Surfactant solubility in Crude the salt oilIFT at solution at Example Surfactant formulation Salt solution [° API]temperature temperature 1 0.11% surfactant Salt content ~148 200 25.90.079 mN/m Slightly mixture of C16C18- ppm with 585 ppm of at 60° C.scattering at 3PO-10EO- divalent cations (14.4% 60° C. CH₂CO₂Na:C16C18-NaCl, 0.15% KCl, 0.15% 3PO-10EO-H (80 MgCl₂ × 6 H₂O, 0.15% mol %:20 mol%)^(a)) CaCl₂ × 2 H₂O, 0.15% (Na₂SO₄) C2 0.1% Salt content ~103 13025.9 >1 mN/m Insoluble at dodecylbenzenesulfonate ppm with 3513 ppm ofat 60° C. 60° C. sodium salt^(b)) divalent cations (8.98% NaCl, 0.11%KCl, 0.90% MgCl₂ × 6 H₂O, 0.90% CaCl₂ × 2 H₂O, 0.11% Na₂SO₄) C3 0.1%Salt content ~103 130 25.9 >1 mN/m Insoluble at dodecylbenzenesulfonateppm with 3513 ppm of at 80° C. 80° C. sodium salt^(b)) divalent cations(8.98% NaCl, 0.11% KCl, 0.90% MgCl₂ × 6 H₂O, 0.90% CaCl₂ × 2 H₂O, 0.11%Na₂SO₄) 4 0.22% surfactant Salt content ~29 910 25.9 0.089 mN/m Clear atmixture of C16C18- ppm with 117 ppm of at 60° C. 60° C. 7PO-4EO-divalent cations (2.88% CH₂CO₂Na:C16C18- NaCl, 0.03% KCl, 0.03%7PO-4EO-H (61 MgCl₂ × 6 H₂O, 0.03% mol %:39 mol %)^(c)) CaCl₂ × 2 H₂O,0.03% Na₂SO₄) 5 0.22% surfactant Salt content ~69 580 25.9 0.072 mN/mSlightly mixture of C16C18C20- ppm with 273 ppm of at 100° C. scatteringat Guerbet-10EO- divalent cations (6.72% 100° C. CH₂CO₂Na:C16C18C NaCl,0.07% KCl, 0.07% 20-Guerbet-10EO-H (85 MgCl₂ × 6 H₂O, 0.07% mol %:15 mol%)^(d)) CaCl₂ × 2 H₂O, 0.07% Na₂SO₄) 6 0.22% surfactant Salt content ~65670 25.9 0.021 mN/m Slightly mixture of ppm with 2236 ppm of at 100° C.scattering at C16C18C20-Guerbet- divalent cations (5.71% 100° C. 10EO-NaCl, 0.07% KCl, 0.57% CH₂CO₂Na:C16C18C20- MgCl₂ × 6 H₂O, 0.57%Guerbet-10EO-H (85 CaCl₂ × 2 H₂O, 0.07% mol %:15 mol %)^(d)) Na₂SO₄) C70.11% surfactant Salt content ~69 580 ppm 25.9 0.332 mN/m Clear atmixture of C16C18- with 273 ppm of at 60° C. 60° C. 3PO-10EO- divalentcations (6.72% CH₂CO₂Na:C16C18- NaCl, 0.07% KCl, 0.07% 3PO-10EO-H (25MgCl₂ × 6 H₂O, 0.07% mol %:75 mol %)^(e)) CaCl₂ × 2 H₂O, 0.07% Na₂SO₄)C8 0.22% surfactant Salt content ~29 910 ppm 25.9 0.536 mN/m Clear atmixture of C16C18- with 117 ppm of at 60° C. 60° C. 7PO-4EO- divalentcations (2.88% CH₂CO₂Na:C16C18- NaCl, 0.03% KCl, 0.03% 7PO-4EO-H (40MgCl₂ × 6 H₂O, 0.03% mol %:60 mol %)^(f)) CaCl₂ × 2 H₂O, 0.03% Na₂SO₄) 90.11% surfactant Salt content ~140 700 25.9 0.007 mN/m Slightly mixtureof C16C18- ppm with 4957 ppm of at 60° C. scattering at 3PO-10EO-divalent cations (12.2% 60° C. CH₂CO₂Na:C16C18- NaCl, 0.15% KCl, 1.27%3PO-10EO-H (80 MgCl₂ × 6 H₂O, 1.27% mol %:20 mol %)^(a)) CaCl₂ × 2 H₂O,0.15% Na₂SO₄) 10  0.22% surfactant Salt content ~30 780 38 0.003 mN/mSlightly mixture of C16C18- ppm with 155 ppm of at 92° C. scattering at7PO-10EO- divalent cations 92° C. CH₂CO₂Na:C16C18- 3PO-10EO-H (70 mol%:30 mol %)^(g)) ^(a))Derived from alkyl ether carboxylate/alkyl etheralcohol mixture 1 b); corresponds to surfactant mixture of 80 mol % ofsurfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(x)—CH₂CO₂M and 20 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na.^(b))Dodecylbenzenesulfonate sodium salt (Lutensit A-LBN, active content50%). ^(c))Derived from alkyl ether carboxylate/alkyl ether alcoholmixture 6; corresponds to surfactant mixture of 61 mol % of surfactantof the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 39 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 4, M = Na. ^(d))Derived from alkylether carboxylate/alkyl ether alcohol mixture 8); corresponds tosurfactant mixture of 85 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 15 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x = 0, y = 0 and z = 10, M = Na. ^(e))Producedfrom mixture of 0.0625% of alkyl ether alcohol 1, which corresponds tosurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, and 0.0375% of the alkyl ethercarboxylate/alkyl ether alcohol mixture 1 b), which corresponds tosurfactant mixture of 80 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 20 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na. ^(f))Produced frommixture of 0.052% of alkyl ether alcohol 6, which corresponds tosurfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 4, and 0.148% of the alkyl ethercarboxylate/alkyl ether alcohol mixture 6, which corresponds tosurfactant mixture of 61 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 39 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 4, M = Na. ^(g))Derived from alkylether carboxylate/alkyl ether alcohol mixture 5; corresponds tosurfactant mixture of 70 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 30 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na.

As can be seen in table 2, the alkyl ether carboxylate/alkyl etheralcohol surfactant mixtures in the molar ratio claimed, based on thedifferent alkyl radicals and with different alkoxylation levels, giveinterfacial tensions of <0.1 mN/m at >5.5° C. and a total surfactantconcentration of <0.5% surfactant. This is surprisingly the case if,inter alia, a certain carboxymethylation level is present in the alkylether carboxylate/alkyl ether alcohol surfactant mixture. Comparativeexamples C7 and C8 show that a carboxymethylation level of 25% or 40% isinadequate to lower the interfacial tension to <0.1 mN/m. However, ifexample 4 is compared with comparative example C8, it is apparent that,under identical conditions, the interfacial tension has been lowered to0.089 mN/m (ex. 4) by raising the carboxymethylation level from 40% to61%. The alkyl ether carboxylate/alkyl ether alcohol surfactant mixtureused is based on a linear primary C16C18 fatty alcohol reacted with 7 eqof propylene oxide and 4 eq of ethylene oxide and the correspondingcarboxylate.

Examples 5 and 6 show an alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture based on a primary C16C18C20 Guerbet alcohol (andhence branched alcohol) reacted with 10 eq of ethylene oxide and thecorresponding carboxylate. The carboxymethylation level is 85%. In spiteof challenging test conditions (high temperature of 100° C. moderate oilwith 25.9° API and moderate salinity with salt contents of about6.5-6.9%), interfacial tensions of 0.072 mN/m (ex. 5) and 0.021 mN/m(ex. 6) were achieved. Astonishingly, in spite of the concentration ofdivalent cations being many times higher (2236 ppm vs. 273 ppm), theinterfacial tension in example 6 is lower (0.021 mN/m) than in example 5(0.072 mN/m). Likewise surprising is the good hardness tolerance, sinceno differences in solubility are apparent in spite of the presence ofdivalent cations. The organic sulfonates typically used in tertiarymineral oil production, for example dodecylbenzenesulfonate (comparativeexamples C2 and C3), are hydrolysis-stable but are insoluble on theirown under the conditions chosen (salt content 10.3% with 3513 ppm ofdivalent cations at 60° C. and 80° C. in comparative examples C2 and C3respectively).

Similarly surprising findings are shown by the comparison of example 1and with example 9. The alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture used is based on a linear primary C16C18 fattyalcohol reacted with 3 eq of propylene oxide and 10 eq of ethylene oxideand the corresponding carboxylate. The carboxymethylation level was 80%.At salt contents of about 15% and about 14%, in the case of 4957 ppm ofdivalent cations, it was even possible to achieve ultralow interfacialtensions: 0.007 mN/m in example 9. In the case of lower water hardness(585 ppm of divalent cations in ex. 1) but otherwise analogousconditions, the interfacial tension in ex. 1 was higher but still <0.1mN/m. Surprisingly ultralow interfacial tensions of 0.003 mN/m with alight crude oil (38° API) at high temperature (92° C.) were achieved inex. 10 with the aid of an alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture. The alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture used is based on a linear primary C16C18 fattyalcohol reacted with 7 eq of propylene oxide and 4 eq of ethylene oxideand the corresponding carboxylate. The carboxymethylation level is 70%.The interfacial tension after 3 h, as described, was 0.003 mN/m. After30 min, the interfacial tension was already 0,007 mN/m.

TABLE 3 Interfacial tensions with alkyl ether carboxylate/alkyl etheralcohol surfactant mixture and cosolvent Surfactant solubility in Crudethe salt oil IFT at solution at Example Surfactant formulation Saltsolution [° API] temperature temperature 1 0.11% surfactant Salt content~148 200 25.9 0.079 mN/m Slightly mixture of C16C18- ppm with 585 ppm ofat 60° C. scattering at 3PO-10EO- divalent cations (14.4% 60° C.CH₂CO₂Na:C16C18- NaCl, 0.15% KCl, 0.15% 3PO-10EO-H (80 MgCl₂ × 6 H₂O,0.15% mol %:20 mol %)^(a)) CaCl₂ × 2 H₂O, 0.15% Na₂SO₄) 2 0.11%surfactant Salt content ~148 200 25.9 0.035 mN/m Clear at mixture (ofC16C18- ppm with 585 ppm of at 60° C. 60° C. 3PO-10EO- divalent cations(14.4% CH₂CO₂Na:C16C18- NaCl, 0.15% KCl, 0.15% 3PO-10EO-H (80 MgCl₂ × 6H₂O, 0.15% mol %:20 mol %)^(a))) CaCl₂ × 2 H₂O, 0.15% and 0.03% butylNa₂SO₄) diethylene glycol 3 0.22% surfactant Salt content ~140 770 25.90.019 mN/m Slightly mixture (of C16C18- ppm with 4957 ppm of at 60° C.scattering at 3PO-10EO- divalent cations (12.2% 60° C. CH₂CO₂Na:C16C18-NaCl, 0.15% KCl, 1.27% 3PO-10EO-H (80 MgCl₂ × 6 H₂O, 1.27% mol %:20 mol%)^(a))) CaCl₂ × 2 H₂O, 0.15% and 0.06% butyl Na₂SO₄) diethylene glycolC4 0.22% surfactant Salt content ~140 770 25.9 0.019 mN/m Slightlymixture (of C16C18- ppm with 4957 ppm of at 60° C. scattering at3PO-10EO- divalent cations (12.2% 60° C. CH₂CO₂Na:C16C18- NaCl, 0.15%KCl, 1.27% 3PO-10EO-H (95 MgCl₂ × 6 H₂O, 1.27% mol %:5 mol %)^(b)))CaCl₂ × 2 H₂O, 0.15% and 0.06% butyl Na₂SO₄) diethylene glycol 5 0.22%surfactant Salt content ~30 780 38 0.002 mN/m Slightly mixture (ofC16C18- ppm with 155 ppm of at 92° C. scattering at 7EO-10EO- divalentcations 92° C. CH₂CO₂Na:C16C18- 7PO-10EO-H (81 mol %:19 mol %)^(c))) and0.073% butyl diethylene glycol 6 0.22% surfactant Salt content ~30 78038 0.001 mN/m Slightly mixture (of C16C18- ppm with 155 ppm of at 92° C.scattering at 7PO-10EO- divalent cations 92° C. CH₂CO₂Na:C16C18-7PO-10EO-H (73 mol %:27 mol %)^(d))) and 0.073% butyl diethylene glycol7 0.11% surfactant salt content ~148 200 25.9 0.041 mN/m Slightlymixture (of C16C18C20- ppm with 585 ppm of at 100° C. scattering atGuerbet-18EO- divalent cations (14.4% 100° C. CH₂CO₂Na:C16C18C20- NaCl,0.15% KCl, 0.15% Guerbet-18EO-H (87 MgCl₂ × 6 H₂O, 0.15% mol %:13 mol%)^(e))) CaCl₂ × 2 H₂O, 0.15% and 0.082% butyl Na₂SO₄) diethylene glycol^(a))Derived from alkyl ether carboxylate/alkyl ether alcohol mixture 1b); corresponds to surfactant mixture of 80 mol % of surfactant of thegeneral formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 20 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na. ^(b))Derived fromcomparative alkyl ether carboxylate/alkyl ether alcohol mixture C11;corresponds to surfactant mixture of 95 mol % of surfactant of thegeneral formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂ CO₂M and 5 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na. ^(c))Derived from alkylether carboxylate/alkyl ether alcohol mixture 12; corresponds tosurfactant mixture of 81 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 19 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na. ^(d))Derived from alkylether carboxylate/alkyl ether alcohol mixture 13; corresponds tosurfactant mixture of 73 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 27 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na. ^(e))Derived from alkylether carboxylate/alkyl ether alcohol mixture 7; corresponds tosurfactant mixture of 87 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 13 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇/C₂₀H₄₁, x = 0, y = 0 and z = 18, M = Na.

As can be inferred from table 3, the claimed alkyl ethercarboxylate/alkyl ether alcohol surfactant mixtures, even in thepresence of cosolvent (butyl diethylene glycol BDG), give interfacialtensions of <0.1 mN/m at >55° C. and a total surfactant concentration of<0.5% surfhetant. The comparison of examples 1 and 2 shows thecontribution of butyl diethylene glycol as cosolvent (identicalconditions: ex. 1 without BDG, ex. 2 with BDG). It was possible to lowerthe interfacial tension further from 0.079 to 0.035 mN/m. With referenceto example 3 and comparative example C4, it was found that,surprisingly, a very high carboxymethylation level is not necessarilyadvantageous. Under the harsh saline conditions with salt content about14.1% and nearly 5000 ppm divalent cations (water hardness), an alkylether carboxylate/alkyl ether alcohol surfactant mixture based on alinear primary C16C18 fatty alcohol reacted with 3 eq of propylene oxideand 10 eq of ethylene oxide, having a carboxymethylation level of 80%(ex. 3), in the presence of BDG, gives an interfacial tension of 0.019mN/m with a moderate crude oil (25.9° API) at 60° C. (ex. 3), whereas,under analogous conditions, a corresponding surfactant mixture having acarboxymethylation level of 95%, which is not in accordance with theinvention, only gives an interfacial tension of 0.109 mN/m.

Ultralow interfacial tensions can be achieved by claimed surfactantformulations as shown in examples 5 and 6. Alkyl ether carboxylate/alkylether alcohol surfactant mixtures based on a linear primary C16C18 fattyalcohol reacted with 7 eq of propylene oxide and 10 eq of ethylene oxideand the corresponding carboxylate, blended with butyl diethylene glycol,lead to 0.001 mN/m (ex. 5) and 0.002 mN/m (ex. 6)—i.e. to ultralowinterfacial tensions. These are astonishingly low values consideringthat the carboxymethylation level of the alkyl ether carboxylate/alkylether alcohol mixture is only 81% (ex. 5) or even only 73% (ex. 6). Inaddition, harsh conditions are present, since temperatures are high (92°C.—because of the elevated fluctuation of the oil-water interface atthis temperature, it is difficult to achieve low interfacial tensionswith just one surfactant or two very similar surfactants) and the use ofalkali is inadvisable because of the water hardness (precipitation wouldlead to blockage of the formation).

Example 7 shows an alkyl ether carboxylate/alkyl ether alcoholsurfactant mixture based on a primary C16C18C20 Guerbet alcohol (andhence branched alcohol) reacted with 18 eq of ethylene oxide and thecorresponding carboxylate. The carboxymethylation level is 87%. In spiteof challenging test conditions (high temperature of 100° C., moderateoil with 25.9° API and high salinity with salt contents of about 14.8%),in the presence of butyl diethylene glycol, an interfacial tension of0.041 mN/m was achieved.

TABLE 4 Interfacial tensions with alkyl ether carboxylate/alkyl etheralcohol surfactant mixture and cosurfactant (and optionally withcosolvent) Surfactant solubility in Crude the salt oil IFT at solutionat Example Surfactant formulation Salt solution [° API] temperaturetemperature 1 0.11% surfactant Salt content ~129 000 29.6 0.009 mN/mClear at mixture (of C16C18- ppm with 10 820 ppm of at 67° C. 67° C.7PO-10EO- divalent cations CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol%)^(a))) and 0.037% butyl diethylene glycol and 0.146% Glucopon225DK^(b)) 2 0.11% surfactant Salt content ~30 780 38 0.007 mN/m Clearat mixture (of C16C18- ppm with 155 ppm of at 92° C. 92° C. 7PO-10EO-divalent cations CH₂CO₂Na:C16C18- 7PO-10EO-H (81 mol %:19 mol %)^(c)))and 0.037% butyl diethylene glycol and 0.146% Glucopon 225DK^(b)) 30.11% surfactant Salt content ~103 130 29.6 0.045 mN/m Clear at mixture(of C16C18- ppm with 3513 ppm of at 80° C. 80° C. 3PO-10EO- divalentcations (8.98% CH₂CO₂Na:C16C18- NaCl, 0.11% KCl, 0.90% 3PO-10EO-H (80MgCl₂ × 6 H₂O, 0.90% mol %:20 mol %)^(d))) CaCl₂ × 2 H₂O, 0.11% and0.146% Hostapur (Na₂SO₄) SAS 30^(e)) ^(a))Derived from alkyl ethercarboxylate/alkyl ether alcohol mixture 13; corresponds to surfactantmixture of 73 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(x)—CH₂CO₂M and 27 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(x)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na. ^(b))Alkyl polyglucoside(based on alkyl radical having 8 to 10 carbon atoms) with activeingredient content 68.3%. ^(c))Derived from alkyl ethercarboxylate/alkyl ether alcohol mixture 12; corresponds to surfactantmixture of 81 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 19 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na. ^(d))Derived from alkylether carboxylate/alkyl ether alcohol mixture 1 b); corresponds tosurfactant mixture of 80 mol % of surfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 20 mol% of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 3 and z = 10, M = Na. ^(e))Secondaryalkanesulfonate sodium salt having 14 to 17 carbon atoms and havingactive ingredient content 32.3%

As can be seen in table 4, the claimed alkyl ether carboxylate/alkylether alcohol surfactant mixtures, even in the presence of cosurfactants(optionally also in the additional presence of cosolvent), giveinterfacial tensions of <0.1 mN/m at >55° C. and a total surfactantconcentration of <0.5% surfactant. As shown by examples 1 and 2, theclaimed alkyl ether carboxylate/alkyl ether alcohol surfactant mixturesbased on a linear primary C16C18 fatty alcohol reacted with 7 eq ofpropylene oxide and 10 eq of ethylene oxide and the correspondingcarboxylate, in the presence of butyl diethylene glycol and aC8C10-based alkyl polyglucoside (Glucopon DK. 225), even lead toultralow interfacial tensions of 0.009 and 0.007 mN/m respectively. Ascan be seen, there are distinct differences in the conditions. Inexample 1, there is a high salinity (salt content about 12.9%) with veryhigh hardness (>10,000 ppm of divalent cations), a moderate crude oil(29.6° API) and elevated temperature (67° C.). In example 2, incontrast, the salinity and water hardness is moderate for EORapplications (30 780 ppm of TDS and 155 ppm of divalent cations), thecrude oil is light (30° API), but the temperature is high (92° C.)Moreover, the ratio of alkyl ether carboxylate to alkyl ether alcoholvaries (73:27 and 81:19 mol %). If example 2 in table 4 is compared withexample 5 in table 3, it can be seen that the conditions are verysimilar but the presence of Glucopon 225 DK leads to clear aqueoussurfactant solutions. On the other hand, the interfacial tension issomewhat higher but still in the ultralow range.

Example 3 in table 4 indicates that it is also possible to use organicsulfonates, for example the secondary C14C17 paraffinsulfonate (HostapurSAS 30) as cosurfactant. However, as compared with examples 1 and 2, analkyl ether carboxylate/alkyl ether alcohol surfactant mixture having alower propoxylation level (3 rather than 7 propoxy units) and nocosolvent was used. The interfacial tension, at 0.045 mN/m, is below 0.1mN/m.

TABLE 5 Interfacial tensions with alkyl ether carboxylate/alkyl etheralcohol surfactant mixture and cosolvent over a broad temperature rangeSurfactant solubility in Crude the salt oil IFT at solution at ExampleSurfactant formulation Salt solution [° API] temperature temperature 10.15% surfactant Salt content ~79 450 38 0.004 mN/m Clear at mixture (ofC16C18- ppm with ~310 ppm of at 60° C. 60° C. 7PO-10EO- divalent cationsCH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol %)^(a))) and 0.05% butyldiethylene glycol 2 0.15% surfactant Salt content ~79 450 38 0.006 mN/mSlightly mixture (of C16C18- ppm with ~310 ppm of at 90° C. scatteringat 7PO-10EO- divalent cations 90° C. CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol%:27 mol %)^(a))) and 0.05% butyl diethylene glycol 3 0.15% surfactantSalt content ~49 670 29 0.005 mN/m Slightly mixture (of C16C18- ppm with~195 ppm of at 90° C. scattering at 7PO-10EO- divalent cations 90° C.CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol %)^(a))) and 0.05% butyldiethylene glycol 4 0.15% surfactant Salt content ~49 670 29 0.006 mN/mSlightly mixture (of C16C18- ppm with ~195 ppm of at 110° C. scatteringat 7PO-10EO- divalent cations 110° C. CH₂CO₂Na:C16C18- 7PO-10EO-H (73mol %:27 mol %)^(a))) and 0.05% butyl diethylene glycol ^(a))Derivedfrom alkyl ether carboxylate/alkyl ether alcohol mixture 13; correspondsto surfactant mixture of 73 mol % of surfactant of the general formula(I) R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 27mol % of surfactant of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na.

As can be seen in table 5, the claimed alkyl ether carboxylate/alkylether alcohol surfactant mixtures blended with butyl diethylene glycolgive ultralow interfacial tensions of <0.01 mN/m over a broadtemperature range. For instance, the same surfactant mixture in the samesaltwater at 60° C. gives an interfacial tension of 0.004 mN/m(example 1) and at 90° C. an interfacial tension of 0.006 mN/m (example2). In a different saltwater and against a different crude oil, the samesurfactant mixture at 90° C. gives an interfacial tension of 0.005 mN/m(example 3) and at 110° C. an interfacial tension of 0.006 mN/m (example4).

Continuative test results for solubility arid for interfacial tensionafter 3-8 h are shown in table 6.

TABLE 6 Interfacial tensions with alkyl ether carboxylate - alkyl etheralcohol surfactant mixture and cosolvent over a broad range of oil andsalinity Surfactant solubility in Crude the salt oil IFT at solution atExample Surfactant formulation Salt solution [° API] temperaturetemperature 1 0.15% surfactant ~49670 ppm salt content 38 0.007 mN/mSlightly mixture (of C16C18- with ~195 ppm divalent at 110° C.scattering at 7PO-10EO- cations 110° C. CH₂CO₂Na:C16C18- 7PO-10EO-H (73mol %:27 mol %)^(a))) and 0.05% butyl diethylene glycol 2 0.15%surfactant ~46830 ppm salt content 38 0.009 mN/m Slightly mixture (ofC16C18- with ~1600 ppm divalent at 110° C. scattering at 7PO-10EO-cations 110° C. CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol %)^(a)))and 0.05% butyl diethylene glycol 3 0.15% surfactant ~49670 ppm saltcontent 29 0.003 mN/m Slightly mixture (of C16C18- with ~195 ppmdivalent at 100° C. scattering at 7PO-10EO- cations 100° C.CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol %)^(a))) and 0.05% butyldiethylene glycol 4 0.15% surfactant ~79450 ppm salt content 38 0.001mN/m Clear at mixture (of C16C18- with ~310 ppm divalent at 80° C. 80°C. 7PO-10EO- cations CH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol%)^(a))) and 0.05% butyl diethylene glycol 5 0.15% surfactant ~64560 ppmsalt content 38 0.008 mN/m Clear at mixture (of C16C18- with ~250 ppmdivalent at 80° C. 80° C. 7PO-10EO- cations CH₂CO₂Na:C16C18- 7PO-10EO-H(73 mol %:27 mol %)^(a))) and 0.05% butyl diethylene glycol 6 0.20%surfactant ~29780 ppm salt content 38 0.002 mN/m Clear at mixture (ofC16C18- with ~1500 ppm divalent at 90° C. 90° C. 7PO-10EO- cationsCH₂CO₂Na:C16C18- 7PO-10EO-H (73 mol %:27 mol %)^(a))) and 0.07% butyldiethylene glycol ^(a))derived from alkyl ether carboxylate/alkyl etheralkocol-mixture 13; corresponds to surfactant mixture of 73 mol % ofsurfactant of the general formula (I)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—CH₂CO₂M and 27 mol% of surfactant of general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H with R¹ =C₁₆H₃₃/C₁₈H₃₇, x = 0, y = 7 and z = 10, M = Na.

As can be seen in table 6, the claimed alkyl ether carboxylate-alkylether alcohol surfactant mixtures blended with butyl diethylene glycolgive ultralow interfacial tensions of <0.01 mN/m over a broad range ofoil and salinity. For instance, the same surfactant mixture in each caseat 110° C. and with the same oil gives a interfacial tension of 0.007mN/m (example 1), a interfacial tension of 0.009 mN/m (example 2)respectively, in two saltwaters. The salinities of both saltwaters arecomparable (˜49,670 ppm vs. 46,830 ppm salt contenz) but the proportionof divalent cations in example 2 is eight-fold higher tha in example 1(˜195 ppm vs. 1600 ppm). Example 6 shows that the same surfactantmixture also with low salt contents (˜29,780 ppm salt content) with highproportion of divalent cations (˜1500 ppm) results in a low interfacialtension of 0.002 mN/m. This is very surprising, as anionic surfactantsare typically very sensitive to multivalent cations. Example 3 comparedto example 1 shows that the same surfactant mixture in the samesaltwater at comparable temperatures also results with different oils(29° API in example 3, all other examples 38° API) in lower interfacialtensions: 0.003 mN/m (example 3).

The same surfactant mixture results in another saltwater and withanother crude oil at 90° C. in an interfacial tension of 0.005 mN/m(example 3) and at 110° C. in a interfacial tension of 0.006 mN/m(example 4).

Examples 4 and 5 show that the same surfactant mixture result at thesame temperature of 80° C. with the same oil in lower interfacialtensions of <0.01 mN/m, also with different salinities (˜79,450 ppm vs.64,560 ppm salt content).

1-45. (canceled)
 46. A method for producing a surfactant mixture bycarboxymethylation comprising at least one anionic surfactant (A) of thegeneral formula (I)R¹—O—(CH₂C(R²)HO)_(x),—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z),—CH₂CO₂M   (I)and at least one nonionic surfactant (B) of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H   (II), where amolar ratio of anionic surfactant (A) to nonionic surfactant (B) of51:49 to 92:8 is present in the surfactant mixture and the nonionicsurfactant (B) serves as starting material for the anionic surfactant(A), where R¹ is a primary linear or branched, saturated or unsaturated,aliphatic hydrocarbyl radical having 10 to 36 carbon atoms; and R² is alinear saturated aliphatic hydrocarbyl radical having 2 to 14 carbonatoms; and M is H, Na, K or NH₄; and x is a number from 0 to 10; and yis a number from 0 to 50; and z is a number from 1 to 35; where the sumtotal of x+y+z is a number from 3 to 80 and the N+y+z alkoxylate groupsmay be arranged in random distribution, in alternation or in blocks; andwhere the sum total of x+y is a number >0 if R¹ is a primary linear,saturated or unsaturated, aliphatic hydrocarbyl radical having 10 to 36carbon atoms, wherein at least one of the following reaction conditionsis used: I) preparing the anionic surfactant (A) of the general formula(I) in a reactor by reacting the nonionic surfactant (B) of the generalformula (II), while stirring, with chloroacetic acid or chloroaceticacid sodium salt in the presence of alkali metal hydroxide or aqueousalkali metal hydroxide, with removal of water of reaction such that thewater content in the reactor is kept at a value of 0.2% to 1.7% duringthe carboxymethylation by applying reduced pressure and/or by passingnitrogen through; II) using aqueous NaOH as alkali metal hydroxide andaqueous chloroacetic acid in a carboxymethylation, using NaOH inrelation to the chloroacetic acid in a ratio of 2 eq:1 eq to 2.2 eq:1eq; and preparing the nonionic surfactant (B) either via abase-catalyzed alkoxylation using KOH or NaOH or CsOH or via analkoxylation using a double metal cyanide catalyst, and the alkoxylationcatalyst is not neutralized and is not removed after the alkoxylationhas ended; and initially charging the nonionic surfactant (B) of thegeneral formula (II) in the reactor in the carboxymethylation and thesodium hydroxide and chloroacetic acid are metered in in parallel at atemperature of 60-110° C. over a period of 1-7 h, the metered additionover the entire period being effected continuously or in equal portionsevery hour, and the stoichiometric ratio of nonionic surfactant (B) ofthe general formula (II) to the chloroacetic acid being 1 eq:1 eq to 1eq:1.9 eq; and the water content in the reactor is kept predominantly atan average value of 0.2% to 1.7% during the carboxymethylation byapplying reduced pressure and/or by passing nitrogen through; III) usingNaOH as alkali metal hydroxide and chloroacetic acid sodium salt areused in the carboxymethylation, using NaOH in relation to thechloroacetic acid sodium salt in a ratio of 1 eq:1 eq to 1 eq:1.9 eq;and preparing the nonionic surfactant (B) via a base-catalyzedalkoxylation using KOH or NaOH or CsOH and is used in unneutralized formin the carboxymethylation; and initially charging the nonionicsurfactant (B) of the general formula (II) in a reactor in thecarboxymethylation together with NaOH or aqueous NaOH, where thestoichiometric ratio of nonionic surfactant (B) of the general formula(II) to NaOH is 1 eq:1 eq to 1 eq:1.5 eq, a temperature of 60-110° C. isset, and the nonionic surfactant (B) of the general formula (II) isconverted to the corresponding sodium saltR¹—O—(CH₂C(R²)HO),—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—Na by applyingreduced pressure and/or passing nitrogen through and, at a temperatureof 60-110° C., the chloroacetic acid sodium salt is metered incompletely or over a period of 4-12 h, where the stoichiometric ratio ofnonionic surfactant (B) of the general formula (II) to the chloroaceticacid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq and where the meteredaddition over the entire period is effected continuously or in equalportions every hour; and the water content in the reactor is kept at avalue of 0.2% to 1.7% during the carboxymethylation by applying reducedpressure and/or by passing nitrogen through; IV) using solid NaOH asalkali metal hydroxide and chloroacetic acid sodium salt in thecarboxymethylation, using NaOH in relation to the chloroacetic acidsodium salt in a ratio of 1 eq:1 eq to 1.1 eq:1 eq; and preparing thenonionic surfactant (B) via a base-catalyzed alkoxylation using KOH orNaOH or CsOH and then neutralized with acetic acid and is used in thecarboxymethylation together with initially 0.5-1.5% water; and initiallycharging chloroacetic acid sodium salt and the nonionic surfactant (B)of the general formula (II) together in a reactor in thecarboxymethylation, where the stoichiometric ratio of nonionicsurfactant (B) of the general formula (II) to the chloroacetic acidsodium salt is 1 eq:1 eq to 1 eq:1.9 eq, and the sodium hydroxide ismetered in at a temperature of 20-70° C. over a period of 4-12 h, themetered addition being effected continuously over the entire period orin equal portions every hour; and the water content in the reactor iskept at a value of 0.2% to 1.7% during the carboxymethylation byapplying reduced pressure and/or by passing nitrogen through; V) usingSolid NaOH as alkali metal hydroxide and chloroacetic acid sodium saltin the carboxymethylation, using NaOH or, in the case of a basicalkoxylate, the sum total of NaOH andR¹—O—(CH₂C(R²)HO)_(x),—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z), —K or the sumtotal in the case of a basic alkoxylate of NaOH andR¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z), —Na or, in thecase of a basic alkoxylate, the sum total of NaOH andR¹—O—(CH₂C(R₂)HO)_(x)—(CH₂C(CH3)HO)_(y)—(CH₂CH₂O)_(z), —Cs in relationto the chloroacetic acid sodium salt in a ratio of 1.1 eq:1 eq to 1eq:1.5 eq, where the ratio of nonionic surfactant (B) of the generalformula (II):NaOH is from 1 eq:1 eq to 1 eq:1.5 eq; and preparing thenonionic surfactant (B) via a base-catalyzed alkoxylation using KOH orNaOH or CsOH or a mixture of NaOH and KOH, and is used in thecarboxymethylation either in neutralized and filtered (i.e. salt-free)form or in the form of an unneutralized basic alkoxylate; and initiallycharging chloroacetic acid sodium salt and the nonionic surfactant (B)of the general formula (II) together in the reactor in thecarboxymethylation, where the stoichiometric ratio of nonionicsurfactant (B) of the general formula (II) to the chloroacetic acidsodium salt is 1 eq:1 eq to 1 eq 1.9 eq, and the sodium hydroxide ismetered in at a temperature of 20-70° C. over a period of 4-12 h, themetered addition being effected continuously over the entire period orin equal portions every hour; and the water content in the reactor iskept at a value of 0.2% to 1.7% during the carboxymethylation byapplying reduced pressure and/or by passing nitrogen through; VI) usingsolid NaOH as alkali metal hydroxide and chloroacetic acid sodium saltin the carboxymethylation, using NaOH in relation to the chloroaceticacid sodium salt in a ratio of 1 eq:1 eq to 1.1 eq:1 eq; and preparingthe nonionic surfactant (B) via an alkoxylation using double metalcyanide catalysis; and initially charging chloroacetic acid sodium saltand the nonionic surfactant (B) of the general formula (II) together inthe reactor in the carboxymethylation, where the stoichiometric ratio ofnonionic surfactant (B) of the general formula (II) to the chloroaceticacid sodium salt is 1 eq:1 eq to 1 eq:1.9 eq, and the sodium hydroxideis metered in at a temperature of 20-70° C. over a period of 4-12 h, themetered addition being effected continuously over the entire period orin equal portions every hour; and the water content in the reactor iskept at a value of 0.2% to 1.7% during the carboxymethylation byapplying reduced pressure and/or by passing nitrogen through.
 47. Themethod of claim 46, wherein a molar ratio of anionic surfactant (A) tononionic surfactant (B) of 60:40 to 92:8 is present in the surfactantmixture on injection and the nonionic surfactant (B) serves as startingmaterial for the anionic surfactant (A).
 48. The method according toclaim 46, wherein a molar ratio of anionic surfactant (A) to nonionicsurfactant (B) of 60:40 to 92:8, is present in the surfactant mixture oninjection, the nonionic surfactant (B) serves as starting material forthe anionic surfactant (A), and the interfacial tension between oil andwater is lowered to <0.05 mN/m at deposit temperature.
 49. The methodaccording to claim 48, wherein a molar ratio of anionic surfactant (A)to nonionic surfactant (B) of 70:30 to 89:11 is present in thesurfactant mixture on injection, the nonionic surfactant (B) serves asstarting material for the anionic surfactant (A), and the interfacialtension between oil and water is lowered to <0.01 mN/m.
 50. The methodaccording to claim 46, wherein R¹ is a primary linear or branched,saturated or unsaturated, aliphatic hydrocarbyl radical having 10 to 36carbon atoms; and R² is a linear saturated aliphatic hydrocarbyl radicalhaving 2 to 14 carbon atoms; and M is H, Na, K or NH₄; and x is a numberfrom 1 to 10; and y is a number from 0 to 50; and z is a number from 3to 35; where the sum total of x+y+z is a number from 4 to
 80. 51. Themethod according to claim 46, wherein R¹ is a primary branched saturatedaliphatic hydrocarbyl radical having 10 to 36 carbon atoms; and R² is alinear saturated aliphatic hydrocarbyl radical having 2 to 14 carbonatoms; and M is H, Na, K or NH₄; and x is a number from 0 to 10; and yis the number 0; and z is a number from 3 to 35; where the sum total ofx+y+z is a number from 3 to
 45. 52. The method according to claim 46,wherein R¹ is a primary branched saturated aliphatic hydrocarbyl radicalhaving 16 to 20 carbon atoms; and x is the number
 0. 53. The methodaccording to claim 46, wherein R¹ is a primary branched saturatedaliphatic hydrocarbyl radical having 16 to 20 carbon atoms selected from2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl or a mixtureof the hydrocarbyl radicals mentioned; and x is the number
 0. 54. Themethod according to claim 46, wherein R¹ is a primary branched saturatedaliphatic hydrocarbyl radical having 24 to 28 carbon atoms, beingselected from the group consisting of 2-decyltetradecyl,2-dodecylhexadecyl, 2-decylhexadecyl, 2-dodecyltetradecyl and a mixtureof the hydrocarbyl radicals mentioned; and x is the number
 0. 55. Themethod according to claim 46, wherein R¹ is a primary linear orbranched, saturated or unsaturated, aliphatic hydrocarbyl radical having10 to 36 carbon atoms; and x is the number 0; and y is a number from 3to 25; and z is a number from 3 to 30; and the sum total of x+y+z is anumber from 6 to
 55. 56. The method of claim 46, wherein x is the number0; and y is a number from 3 to 10; and z is a number from 4 to 15; andthe sum total of x+y+z is a number from 7 to
 25. 57. The method of claim46, wherein R¹ is a primary linear or branched, saturated orunsaturated, aliphatic hydrocarbyl radical having 13 to 20 carbon atoms.58. The method according to claim 46, wherein R¹ is a primary linearsaturated aliphatic hydrocarbyl radical having 16 to 18 carbon atoms.59. The method according to claim 46, wherein the sum total of x+y+z isa number from 7 to
 24. 60. A concentrate with a surfactant mixturecomprising at least one anionic surfactant (A) of the general formula(I)R¹—O—(CH₂C(R²)HO)_(x),—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)₂,—CH₂CO₂M   (I) andat least one nonionic surfactant (B) of the general formula (II)R¹—O—(CH₂C(R²)HO)_(x)—(CH₂C(CH₃)HO)_(y)—(CH₂CH₂O)_(z)—H   (II) where amolar ratio of anionic surfactant (A) to nonionic surfactant (B) of51:49 to 92:8 is present in the surfactant mixture on injection and thenonionic surfactant (B) serves as starting material for the anionicsurfactant (A), where R¹ is a primary linear or branched, saturated orunsaturated, aliphatic hydrocarbyl radical having 10 to 36 carbon atoms;and R² is a linear saturated aliphatic hydrocarbyl radical having 2 to14 carbon atoms; and M is H, Na, K or NH₄; and x is a number from 0 to10; and y is a number from 0 to 50; and z is a number from 1 to 35;where the sum total of x+y+z is a number from 3 to 80 and the x+y+zalkoxylate groups may be arranged in random distribution, in alternationor in blocks; and where the sum total of x+y is a number >0 if R¹ is aprimary linear, saturated or unsaturated, aliphatic hydrocarbyl radicalhaving 10 to 36 carbon atoms, wherein the concentrate comprises 20% byweight to 70% by weight of the surfactant mixture, 10% by weight to 40%by weight of water and 10% by weight to 40% by weight of a cosolvent,based on the total amount of the concentrate, where a) the cosolvent isselected from the group of the aliphatic alcohols having 3 to 8 carbonatoms or from the group of the alkyl monoethylene glycols, the alkyldiethylene glycols or the alkyl triethylene glycols, where the alkylradical is an aliphatic hydrocarbyl radical having 3 to 6 carbon atoms;and/or b) the concentrate is free-flowing at 20° C. and has a viscosityat 40° C. of <1500 mPas at 200 Hz.
 61. The concentrate of claim 60,wherein the concentrate comprises 0.5% to 15% by weight of a mixturecomprising NaCl and diglycolic acid disodium salt, where NaCl is presentin excess relative to diglycolic acid disodium salt.
 62. The concentrateof claim 60, wherein the concentrate comprises butyl diethylene glycolas cosolvent.
 63. The concentrate of claims 62, wherein R¹ is a primarylinear or branched, saturated or unsaturated, aliphatic hydrocarbylradical having 10 to 36 carbon atoms; and R² is a linear saturatedaliphatic hydrocarbyl radical having 2 to 14 carbon atoms; and M is H,Na, K or NH₄; and x is a number from 1 to 10; and y is a number from 0to 50; and z is a number from 3 to 35; where the sum total of x+y+z is anumber from 4 to
 80. 64. The concentrate according to claim 60, whereinR¹ is a primary branched saturated aliphatic hydrocarbyl radical having10 to 36 carbon atoms; and R² is a linear saturated aliphatichydrocarbyl radical having 2 to 14 carbon atoms; and M is H, Na, K orNH₄; and x is a number from 0 to 10; and y is the number 0; and z is anumber from 3 to 35; where the sum total of x+y+z is a number from 3 to45.
 65. The concentrate according to claim 60, wherein R¹ is a primarybranched saturated aliphatic hydrocarbyl radical having 16 to 20 carbonatoms, and is selected from the group consisting of 2-hexyldecyl,2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl and a mixture of thehydrocarbyl radicals mentioned; and x is the number
 0. 66. Theconcentrate according to claim 60, wherein R¹ is a primary branchedsaturated aliphatic hydrocarbyl radical having 24 to 28 carbon atoms,being 2-decyltetradecyl, 2-dodecylhexadecyl, 2-decylhexadecyl or2-dodecyltetradecyl or a mixture of the hydrocarbyl radicals mentioned;and x is the number
 0. 67. The concentrate according to claim 60,wherein R¹ is a primary linear or branched, saturated or unsaturated,aliphatic hydrocarbyl radical having 10 to 36 carbon atoms; and x is thenumber 0; and y is a number from 3 to 25; and z is a number from 3 to30; and the sum total of x+y+z is a number from 6 to
 55. 68. Theconcentrate as claimed in claim 60, wherein x is the number 0; and y isa number from 3 to 10; and z is a number from 4 to 15; and the sum totalof x+y+z is a number from 7 to
 25. 69. The concentrate according toclaim 60, wherein R¹ is a primary linear or branched, saturated orunsaturated, aliphatic hydrocarbyl radical having 13 to 20 carbon atoms.70. The concentrate according to claim 60, wherein R¹ is a primarylinear saturated aliphatic hydrocarbyl radical having 16 to 18 carbonatoms.
 71. The concentrate according to claim 60, wherein the sum totalof x+y+z is a number from 7 to 24.